Question

give me answere 14?????????

Answer 1

8x=pie
7x+x=pie
7x=pie-x :taking cos both sides
cos7x=cos(pie-x)
cos7x=-cos(pie)
so you got the value of cos7x now put on this to 2nd equation ie
cos7x+cosx=-cosx+cosx =0 hence proved ❤

Answer 2

Let me take @ as x for convenience.

Hence, 8x = pi.

x = pi/8.

.

Therefore LHS of To prove:-

.

= Cosx + Cos(7x)

= Cos(pi/8) + Cos (7pi/8)

= Cos(pi/8) + Cos[(8pi - pi)/8]

= Cos(pi/8) + Cos[pi - (pi/8)]

Here Cos(pi - pi/8) = -Cos(pi/8).

= Cos(pi/8) + Cos(pi - pi/8)

= Cos(pi/8) - Cos(pi/8)

= 0

= RHS
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