A Level

MATHEMATICS · Single correct · A Level · Mathematics · Trigonometry · Trigonometry

Problem

f(x)=\cos(\log x)

, then

f(x)f(y)-\frac{1}{2}\left[f\left(\frac{x}{y}\right)+f(xy)\right]=

(1)

-1

(2)

\frac{1}{2}

(3)

-2

(4) None of these