t=tanx/2 substitutions for integralsWatch
But i can't for the life of me work out how they substituted the dx in this part:
This of course comes from:
and I understand therefore why sinx has been substituted but why is dx = 2dt/1+t^2? (shown last on the identity list) Is it just something we're expected to learn and know?
dt/dx = (1/2)sec^2(x/2)
dt = (1/2)(1+t^2)dx
dx = 2dt/(1+t^2)