Question

range of the function f(x)=cos^2x -5cosx-6

Answer 1

cos²x-5cosx-6

cos²x-6cosx+cosx-6

cosx(cosx-6)+1(cosx-6)

(cosx+1)(cosx-6)

cosx=-1

x=180°

cosx=6

impossible

range ={π}