When integrating by trigonometric substitution, what are some useful identities to know?

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Answer 1 · 2014-10-18T16:20:53

Useful Trigonometric Identities

#cos^2theta+sin^2theta=1#

#1+tan^2theta=sec^2theta#

#sin2theta=2sin theta cos theta#

#cos2theta=cos^2theta-sin^2theta=2cos^2theta-1=1-2sin^2theta#

#cos^2theta=1/2(1+cos2theta)#

#sin^2theta=1/2(1-cos2theta)#

I hope that this was helpful.