trigonometry

Question: If $\sin (\theta +\alpha )=a$ and $\sin (\theta +\beta )=b,$ then $\cos 2\,(\alpha -\beta )-4ab\,\cos (\alpha -\beta )$ is equal to

1) $1-{{a}^{2}}-{{b}^{2}}$

2) $1-2{{a}^{2}}-2{{b}^{2}}$

3) $2+{{a}^{2}}+{{b}^{2}}$

4) $2-{{a}^{2}}-{{b}^{2}}$

Solution:

Explanation: No Solution

Trigonometric ratios of sum and difference of two and three

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