Question

answer it fast and don't answer irrelevantly PLEASE ​

Answer 1

Answer:

Step-by-step explanation:

hiii!!! folk..

A+B+C=180°(given)

=)from lhs

cos2A+,cos2B-cos2C

=)2cos(2A+2B)/2*Cos(2A-2B/2)-cos2C

=)2cos(A+B)*cos(A-B)+2cos^2C+1. √【cos2C=2cos,^2C+1】

=)2cos(π-C)*cos(A-B)+2cos,^2+1

=)1-2cosC/2(cosA-B)+cos【π-(A+B)】

=)1-2CosC/2(cosA-B)-cosC(A+B)

=)1-2cosC(2sin(A-B+A+B/2)*sin(,A+B-A+B)/2

=)1-2cosC(2sunA*sinB)

=)1-4sinA*sinB*sinC=Rhs.prooved.

hope it help you.