Okay so this question is on my exam study guide for Calculus 1, and I'm having trouble getting to an answer. Here are the steps I have tried currently.
- Given: $y = (cos(x))^ln(x)$
- Logarithmic differentiation: $ln(y) = ln(cos(x)^ln(x))$
- Simplify: $(1/y)*(dy/dx) = ln(x) * ln(cos(x))$
- Simplify: $(1/y)*(dy/dx) = (1/x) * ln(cos(x))$
- Product Rule: $(1/y)*(dy/dx) = (1/x) * ln(cos(x)) + (ln(cos(x)))' * ln(x)$
- Chain Rule: $(1/y)*(dy/dx) = (1/x)*ln(cos(x)) + [1/cos(x) * -sin(x) * ln(x)]$
- Answer: $(dy/dx) = y((1/x)*ln(cos(x)) + [1/cos(x) * -sin(x) * ln(x)])$
Can someone help as to see where I went wrong in my thinking here
we get $$\frac{y'}{y}=\frac{1}{x}\ln(\cos(x))+\ln(x)\cdot \frac{1}{\cos(x)}\cdot (-\sin(x))$$