In a circle a diameter ABAB is drawn and on one side of it an arc CDCD is marked, which subtends an angle 50^@50 at the center. ACAC and BDBD are joined and produced to meet at EE. Find /_CEDCED?

1 Answer
Feb 2, 2017

/_CED=65^@CED=65

Explanation:

Consider the following figure, as described in the question, where we have joined ADAD and BCBC and let /_BOD=xBOD=x and /_AOC=yAOC=y.
enter image source here
As chord BCBC subtends angle /_BOCBOC at center and /_BAEBAE at the circle, we have /_BAE=1/2(50+x)=25+x/2BAE=12(50+x)=25+x2

Similarly for chord ADAD, we have /_ABE=1/2(50+y)=25+y/2ABE=12(50+y)=25+y2

Hence /_CEDCED, being the third angle of DeltaABEΔABE is given by

/_CED=180^@-/_BAE-/_ABECED=180BAEABE

= 180^@-25^@-x/2-25^@-y/2=130^@-(x+y)/218025x225y2=130x+y2

= 130^@-1/2(180^@-50^@)=130^@-65^@=65^@13012(18050)=13065=65