Half-Angle identity (sinfracA2=pmsqrtfrac1-cosA2,cosfracA2=pmsqrtfrac1+cosA2,tanfracA2=fracsi)
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sinfracA2=pmsqrtfrac1-cos A2, cosfracA2=pmsqrtfrac1+cos A2, tanfracA2=fracsin A1
What each symbol means
| Symbol | What it stands for |
|---|---|
| A, B, x, a, b | As 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.