How do you integrate int (theta^2+sec^2theta)d theta(θ2+sec2θ)dθ?

1 Answer
Dec 5, 2016

theta^3/3+tantheta+Cθ33+tanθ+C

Explanation:

I=int(theta^2+sec^2theta)d thetaI=(θ2+sec2θ)dθ

Split up the integral:

I=inttheta^2d theta+intsec^2thetad thetaI=θ2dθ+sec2θdθ

Think of the following two things:

  • intx^ndx=x^(n+1)/(n+1)+Cxndx=xn+1n+1+C
  • d/dxtanx=sec^2x=>intsec^2xdx=tanx+Cddxtanx=sec2xsec2xdx=tanx+C

Don't be tripped up by the use of thetaθ as a variable—this process is identical to integrating int(x^2+sec^2x)dx(x2+sec2x)dx.

Thus:

I=theta^3/3+tantheta+CI=θ33+tanθ+C