If A + B + C = `pi`, then what is cos(A + B) + cos C equal to ?

If A + B + C = pi , then what is cos (A+B) + cosC equal to?

If A + B + C =pi , prove that : cos A + cos B - cos C> 1 .

IF A + B + C = pi then cos ^2 A + cos^2 B + cos^2 C=

If A+ B + C = pi, then cos^(2) A + cos ^(2) B + cos ^(2) C is equal to : A) 1 - cos A cos B cos C B) 1 - 2 cos A cos B cos C C) 2 cos A cos B cos C D) 1 + cos A cos B cos C

If A+B+C =pi, then cos ^(2) A+ cos ^(2)B - cos^(2) C is equal to

If A+B+C =pi, then cos ^(2) A+ cos ^(2)B + cos^(2) C is equal to

If A + B + C =pi , prove that : cos 2A + cos 2B + cos 2C = -1-4 cos A cos B cos C .

If A + B + C = pi , prove that cos A cosec B cosec C + cos B cosec C cosec A + cos C cosec A cosec B = 2 .

If A + B + C =pi , prove that : cos 2A - cos 2B + cos 2C= 1-4 sin A cos B sin C .

If A + B+ C = 3 pi//2 , then the value of cos 2 A + cos 2 B + cos2 C is equal to