Question

If A+B+C=180then cos2A+cos2B+cos2C+1=

Answer 1

Answer:

A+B+C =180 A+B=180-C

singh(A+B) sin C cos(A+B) -cos C

cos 2A +cos 2B cos 2c

2cos(2A + 2B / 2 ) cos (2A-2B/2) +cos 2c

2cos (A+B) cos (A-B) + cos 2c

2(-cos c) cos (A-B) + 2cos2 C-1

-1-2cos c(cos (A-B) -cos c)

-1-2 cos c (cos (A-B) - cos (A+B)

-1-2 cos C (2cos a cos B)

-1-4cos A cos B cos C