If f(x) = cos (log x), then f(x²) f(y²) − 1/2 { f(x²/y²) + f(x² y²) } has the value(a) −2(b) −1(c) 1/2(d) none of these
Find the Value of f(x²)f(y²) Find the Value of the Given Expression Question: If \( f(x)=\cos(\log x) \), then find the value of \[ f(x^2)f(y^2)-\frac12\left\{f\left(\frac{x^2}{y^2}\right)+f(x^2y^2)\right\} \] (a) \(-2\) (b) \(-1\) (c) \(\frac12\) (d) none of these Solution: \[ f(x^2)=\cos(2\log x), \qquad f(y^2)=\cos(2\log y) \] Using \[ 2\cos A\cos B=\cos(A-B)+\cos(A+B) \] \[ f(x^2)f(y^2) = \frac12\left[ f\left(\frac{x^2}{y^2}\right)