Question

sine
$\sin( \alpha )2 \cos( \beta ) 2$
​

Answer 1

Sin, Cos and Tan of Sum and Difference of Two Angles

by M. Bourne

The sine of the sum and difference of two angles is as follows:

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Tan of Sum and Difference of Two Angles

sin(α + β) = sin α cos β + cos α sin β

sin(α − β) = sin α cos β − cos α sin β

The cosine of the sum and difference of two angles is as follows:

cos(α + β) = cos α cos β − sin α sin β

cos(α − β) = cos α cos β + sin α sin β