Double Angle Set identity (sin2A=2sinAcosA;cos2A=cos^2A-sin^2A=2cos^2A-1=1-2sin^2A;tan2A=frac2tanA1)

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sin 2A=2sin Acos A; cos 2A=cos^2A-sin^2A=2cos^2A-1=1-2sin^2A; tan 2A=frac2tan A1

What each symbol means

SymbolWhat it stands for
A, B, x, a, bAs in standard NCERT treatment; domain restrictions apply for tan.

When to use this

Standard NCERT conditions; tan identities exclude odd multiples of π/2 where undefined.