y = (cos x)^(ln x)
ln(y) = ln(x)*ln(cos(x))
Differentiating both sides:
y'/y = -ln(x)*tan(x) + ln(cos(x))/x
y' = [(cos x)^(ln x)]*(-ln(x)*tan(x) + ln(cos(x))/x)
ln(y) = ln(x)*ln(cos(x))
Differentiating both sides:
y'/y = -ln(x)*tan(x) + ln(cos(x))/x
y' = [(cos x)^(ln x)]*(-ln(x)*tan(x) + ln(cos(x))/x)