How do you find the derivatives of y=(sintheta)^tanthetay=(sinθ)tanθ by logarithmic differentiation?

1 Answer
Feb 10, 2017

(dy)/(dx)=(sintheta)^(tantheta)(sec^2thetalnsintheta+1)dydx=(sinθ)tanθ(sec2θlnsinθ+1)

Explanation:

usinf logarithmic differentiation

y=(sintheta)^(tantheta)y=(sinθ)tanθ

lny=ln(sintheta)^(tantheta)lny=ln(sinθ)tanθ

by laws of logs

lny=tanthetaln(sintheta)lny=tanθln(sinθ)

now differentiate wrt" " xwrt x

d/dx(lny=tanthetaln(sintheta))ddx(lny=tanθln(sinθ))

RHS" "RHS will need the product rule

1/y(dy)/(dx)=sec^2thetalnsintheta+tantheta1/sinthetaxxcostheta1ydydx=sec2θlnsinθ+tanθ1sinθ×cosθ

1/y(dy)/(dx)=sec^2thetalnsintheta+cancel((sintheta/costhetaxxcostheta/sintheta))^(=1)

1/y(dy)/(dx)=sec^2thetalnsintheta+1

(dy)/(dx)=y(sec^2thetalnsintheta+1)

(dy)/(dx)=(sintheta)^(tantheta)(sec^2thetalnsintheta+1)