Angle ADB = 180 - (A/2+B)
so ADC=A/2 + B
since sin of both these angles is same we have AB=AC
now ADB is congruent to ADC (SAS rule)
andles ADB and ADC are each equal to 90.
also, angle B = angle C = 90-A/2
.:2cosA/2 = a/b
cosine rule: cosA = b^2+c^2-a^2 / 2bc
cosA = 1 - 1/2 (a/b)^2
= 1 - 2 cos^2A/2
= - cosA
2cosA = 0
cosA=0
A=90
this should be it..
thanks
Moderation Team
![[Post New]](/templates/default/images/icon_minipost_new.gif){kind=icon}
![[Up]](/templates/default/images/icon_up.gif "[Up]"){kind=icon}
236
