Section+3-5

3-5 Double and Half Angle Identities

Double Angle Identities: sin2x=2sinxcosx cos2x=cos^2x-sin^2x cos2x=2cos^2x-1 cos2x=1-2sin^2x tan2x=(2tanx/1-tan^2x)

Examples:

Half Angle Identities: sin(x/2)= (+,-) sqt(1-cosx/2) cos(x/2)= (+,-) sqt(1+cosx/2) tan(x/2)= (+,-) sqt(1-cosx/1+cosx)

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