Question

if sin 2A = sin 2B + sin 2C , prove that either B= 90 or C = 90​

Answer 1

Answer:

sin 2A=2sin(B+C)cos(B-C)

2 sinA cosA=2sinA cos(B-C)

cosA=cos(B-C) or cos (C-B)

A=B-C or A=C-B

A+C=B or A+B=C

A+B+C=2B or A+B+C=2C

180=2B or 180=2C

B=90°or C=90°