The expression (cos 6x+6 cos 4x + 15 cos 2x + 10/cos 5x + 5 cos 3x +10 cos x) is equal to

Question

The expression (cos 6x+6 cos 4x + 15 cos 2x + 10/cos 5x + 5 cos 3x +10 cos x) is equal to (A) cos 2x (B) 2cos x (C) cos2x (D) 1 + cos x.

Tardigrade Admin · Accepted Answer

The given expression can be written as ((cos 6x+cos 4x) + 5(cos 4x + cos 2x)+10(cos 2x+1)/cos 5x + 5 cos 3x +10 cos x) = (2 cos 5x cos x + 5.2 cos 3x cos x + 10.2 cos2 x/cos 5x + 5 cos 3x +10 cos x) = (2 cos x(cos 5x+5 cos 3x + 10 cos x)/cos 5x + 5 cos 3x +10 cos x) = 2 cos x

Q. The expression $\frac{cos 6 x + 6 cos 4 x + 15 cos 2 x + 10}{cos 5 x + 5 cos 3 x + 10 cos x}$ is equal to

$cos 2 x$

$2 cos x$

$co s^{2} x$

$1 + cos x$ .

Q. The expression cos5x+5cos3x+10cosxcos6x+6cos4x+15cos2x+10​ is equal to

cos2x

2cosx