Question

if cos8x=sinx and 8x>90 degree then sec6x is

Answer 1

Answer:

If cos x + sec x = 2, what is the value of cos^10 x + sec^20 x?

Prerequisites:-

secx=1cosx

(x−y)2=x2−2.x.y+y2

Given

cosx+secx=2

Using Prerequisite

cosx+1cosx=2

cos2x+1cosx=2

cos2x+1=2.cosx

cos2x−2.cosx+1=0

Using Prerequisite

(cosx−1)2=0

cosx−1=0

cosx=1

So,

secx=1

cos10x+sec20x

(cosx)10+(secx)20

Putting values of cosxand secx

1+1=2