Right angles in triangles formed in trapezoid

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In the following trapezoid, is angle A in triangle ABC a right angle even though it isn't labeled as such? And if so what property would we use to determine that? I was able to get the correct area for triangle ABC using Heron's formula after finding side AC using the Pythagorean theorem. Therefore, angle A in triangle ABC must be a right angle, but I can't find the property.



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    Using the Pythagorean Theorem on the right triangle AEB to determine EB, calculating CE from the difference in lengths and then finding AC using the Pythagorean Theorem on AEC will enable you to check if CAB is a right triangle.
    – Ron Kaminsky
    5 hours ago















up vote
3
down vote

favorite












In the following trapezoid, is angle A in triangle ABC a right angle even though it isn't labeled as such? And if so what property would we use to determine that? I was able to get the correct area for triangle ABC using Heron's formula after finding side AC using the Pythagorean theorem. Therefore, angle A in triangle ABC must be a right angle, but I can't find the property.



enter image description here










share|cite|improve this question

















  • 1




    Using the Pythagorean Theorem on the right triangle AEB to determine EB, calculating CE from the difference in lengths and then finding AC using the Pythagorean Theorem on AEC will enable you to check if CAB is a right triangle.
    – Ron Kaminsky
    5 hours ago













up vote
3
down vote

favorite









up vote
3
down vote

favorite











In the following trapezoid, is angle A in triangle ABC a right angle even though it isn't labeled as such? And if so what property would we use to determine that? I was able to get the correct area for triangle ABC using Heron's formula after finding side AC using the Pythagorean theorem. Therefore, angle A in triangle ABC must be a right angle, but I can't find the property.



enter image description here










share|cite|improve this question













In the following trapezoid, is angle A in triangle ABC a right angle even though it isn't labeled as such? And if so what property would we use to determine that? I was able to get the correct area for triangle ABC using Heron's formula after finding side AC using the Pythagorean theorem. Therefore, angle A in triangle ABC must be a right angle, but I can't find the property.



enter image description here







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asked 5 hours ago









user27343

322




322







  • 1




    Using the Pythagorean Theorem on the right triangle AEB to determine EB, calculating CE from the difference in lengths and then finding AC using the Pythagorean Theorem on AEC will enable you to check if CAB is a right triangle.
    – Ron Kaminsky
    5 hours ago













  • 1




    Using the Pythagorean Theorem on the right triangle AEB to determine EB, calculating CE from the difference in lengths and then finding AC using the Pythagorean Theorem on AEC will enable you to check if CAB is a right triangle.
    – Ron Kaminsky
    5 hours ago








1




1




Using the Pythagorean Theorem on the right triangle AEB to determine EB, calculating CE from the difference in lengths and then finding AC using the Pythagorean Theorem on AEC will enable you to check if CAB is a right triangle.
– Ron Kaminsky
5 hours ago





Using the Pythagorean Theorem on the right triangle AEB to determine EB, calculating CE from the difference in lengths and then finding AC using the Pythagorean Theorem on AEC will enable you to check if CAB is a right triangle.
– Ron Kaminsky
5 hours ago











3 Answers
3






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oldest

votes

















up vote
2
down vote



accepted










Yes, it is. Because by Pythagorean Theorem on $Delta AEB$, $|EB| = 9$ and therefore $|CE| = 25 - 9 = 16$. Then by Pythagorean Theorem on $Delta AEC$, $|AC| = 20$. Then $Delta ABC$ has sides $15, 20, 25$ which is a Pythagorean triple. Therefore, $angle CAB = 90^circ$.






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    up vote
    1
    down vote













    From the information given it is easy to assess the claim.



    First render $|EB|=9$ with the Pythagorean Theorem on $triangle ABE$. Then render $|CE|=16$ by difference along $overlineCB$. Apply the Pythagorean Theorem to $triangle ACE$ to get $|AE|$ and then check your result against the Pythagorean Theorem in $triangle BCA$. You should find that the claim is true.



    Bonus: Draw the perpendicular to $overlineCB$ from $D$ which intersects $overlineCB$ at $F$ prove that $|DA|=11$ is also correct.






    share|cite|improve this answer



























      up vote
      1
      down vote













      If $$AE^2 = CEtimes EB$$



      then the triangle $ABC$ is a right triangle and the angle $CAB =90$ degrees.



      We have $AE^2 =144$ and it is easy to see that $CEtimes EB =16 times 9 =144$$



      Thus the answer is yes.






      share|cite|improve this answer




















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        3 Answers
        3






        active

        oldest

        votes








        3 Answers
        3






        active

        oldest

        votes









        active

        oldest

        votes






        active

        oldest

        votes








        up vote
        2
        down vote



        accepted










        Yes, it is. Because by Pythagorean Theorem on $Delta AEB$, $|EB| = 9$ and therefore $|CE| = 25 - 9 = 16$. Then by Pythagorean Theorem on $Delta AEC$, $|AC| = 20$. Then $Delta ABC$ has sides $15, 20, 25$ which is a Pythagorean triple. Therefore, $angle CAB = 90^circ$.






        share|cite|improve this answer
























          up vote
          2
          down vote



          accepted










          Yes, it is. Because by Pythagorean Theorem on $Delta AEB$, $|EB| = 9$ and therefore $|CE| = 25 - 9 = 16$. Then by Pythagorean Theorem on $Delta AEC$, $|AC| = 20$. Then $Delta ABC$ has sides $15, 20, 25$ which is a Pythagorean triple. Therefore, $angle CAB = 90^circ$.






          share|cite|improve this answer






















            up vote
            2
            down vote



            accepted







            up vote
            2
            down vote



            accepted






            Yes, it is. Because by Pythagorean Theorem on $Delta AEB$, $|EB| = 9$ and therefore $|CE| = 25 - 9 = 16$. Then by Pythagorean Theorem on $Delta AEC$, $|AC| = 20$. Then $Delta ABC$ has sides $15, 20, 25$ which is a Pythagorean triple. Therefore, $angle CAB = 90^circ$.






            share|cite|improve this answer












            Yes, it is. Because by Pythagorean Theorem on $Delta AEB$, $|EB| = 9$ and therefore $|CE| = 25 - 9 = 16$. Then by Pythagorean Theorem on $Delta AEC$, $|AC| = 20$. Then $Delta ABC$ has sides $15, 20, 25$ which is a Pythagorean triple. Therefore, $angle CAB = 90^circ$.







            share|cite|improve this answer












            share|cite|improve this answer



            share|cite|improve this answer










            answered 5 hours ago









            ArsenBerk

            7,15221234




            7,15221234




















                up vote
                1
                down vote













                From the information given it is easy to assess the claim.



                First render $|EB|=9$ with the Pythagorean Theorem on $triangle ABE$. Then render $|CE|=16$ by difference along $overlineCB$. Apply the Pythagorean Theorem to $triangle ACE$ to get $|AE|$ and then check your result against the Pythagorean Theorem in $triangle BCA$. You should find that the claim is true.



                Bonus: Draw the perpendicular to $overlineCB$ from $D$ which intersects $overlineCB$ at $F$ prove that $|DA|=11$ is also correct.






                share|cite|improve this answer
























                  up vote
                  1
                  down vote













                  From the information given it is easy to assess the claim.



                  First render $|EB|=9$ with the Pythagorean Theorem on $triangle ABE$. Then render $|CE|=16$ by difference along $overlineCB$. Apply the Pythagorean Theorem to $triangle ACE$ to get $|AE|$ and then check your result against the Pythagorean Theorem in $triangle BCA$. You should find that the claim is true.



                  Bonus: Draw the perpendicular to $overlineCB$ from $D$ which intersects $overlineCB$ at $F$ prove that $|DA|=11$ is also correct.






                  share|cite|improve this answer






















                    up vote
                    1
                    down vote










                    up vote
                    1
                    down vote









                    From the information given it is easy to assess the claim.



                    First render $|EB|=9$ with the Pythagorean Theorem on $triangle ABE$. Then render $|CE|=16$ by difference along $overlineCB$. Apply the Pythagorean Theorem to $triangle ACE$ to get $|AE|$ and then check your result against the Pythagorean Theorem in $triangle BCA$. You should find that the claim is true.



                    Bonus: Draw the perpendicular to $overlineCB$ from $D$ which intersects $overlineCB$ at $F$ prove that $|DA|=11$ is also correct.






                    share|cite|improve this answer












                    From the information given it is easy to assess the claim.



                    First render $|EB|=9$ with the Pythagorean Theorem on $triangle ABE$. Then render $|CE|=16$ by difference along $overlineCB$. Apply the Pythagorean Theorem to $triangle ACE$ to get $|AE|$ and then check your result against the Pythagorean Theorem in $triangle BCA$. You should find that the claim is true.



                    Bonus: Draw the perpendicular to $overlineCB$ from $D$ which intersects $overlineCB$ at $F$ prove that $|DA|=11$ is also correct.







                    share|cite|improve this answer












                    share|cite|improve this answer



                    share|cite|improve this answer










                    answered 5 hours ago









                    Oscar Lanzi

                    10.6k11734




                    10.6k11734




















                        up vote
                        1
                        down vote













                        If $$AE^2 = CEtimes EB$$



                        then the triangle $ABC$ is a right triangle and the angle $CAB =90$ degrees.



                        We have $AE^2 =144$ and it is easy to see that $CEtimes EB =16 times 9 =144$$



                        Thus the answer is yes.






                        share|cite|improve this answer
























                          up vote
                          1
                          down vote













                          If $$AE^2 = CEtimes EB$$



                          then the triangle $ABC$ is a right triangle and the angle $CAB =90$ degrees.



                          We have $AE^2 =144$ and it is easy to see that $CEtimes EB =16 times 9 =144$$



                          Thus the answer is yes.






                          share|cite|improve this answer






















                            up vote
                            1
                            down vote










                            up vote
                            1
                            down vote









                            If $$AE^2 = CEtimes EB$$



                            then the triangle $ABC$ is a right triangle and the angle $CAB =90$ degrees.



                            We have $AE^2 =144$ and it is easy to see that $CEtimes EB =16 times 9 =144$$



                            Thus the answer is yes.






                            share|cite|improve this answer












                            If $$AE^2 = CEtimes EB$$



                            then the triangle $ABC$ is a right triangle and the angle $CAB =90$ degrees.



                            We have $AE^2 =144$ and it is easy to see that $CEtimes EB =16 times 9 =144$$



                            Thus the answer is yes.







                            share|cite|improve this answer












                            share|cite|improve this answer



                            share|cite|improve this answer










                            answered 5 hours ago









                            Mohammad Riazi-Kermani

                            33.2k41854




                            33.2k41854



























                                 

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