Question

In any quadrilateral ABCD, find the value of sin(A+B) + sin(C+D)

Answer 1

sin C + sin d= 2 sin (C+d)/2 cos (c-d)/2

SIN ( A+ B)+ SIN (C+D)=2SIN ( A+B+C+D)/COS(A+B-(C+D))/2......1

since (A+B+C+D)/2=360/2

using it eq.1 becomes

2SIN 180°COS(A+B-C-D)/2

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