Prove: $\displaystyle sin^{2}(\alpha -\beta ) = sin^{2}\alpha - sin^{2}\beta +2sin\alpha .sin\beta .cos(\alpha- \beta )$

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- Feb 26th 2011, 10:16 AMarmProving expression with sines.
Prove: $\displaystyle sin^{2}(\alpha -\beta ) = sin^{2}\alpha - sin^{2}\beta +2sin\alpha .sin\beta .cos(\alpha- \beta )$

- Feb 26th 2011, 01:00 PMmr fantastic