Q. $co s^{2} 1 0^{\circ} + co s^{2} 5 0^{\circ} - cos 1 0^{\circ} cos 5 0^{\circ}$ is equal to

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A

$\frac{3}{4}$

B

$\frac{3}{2}$

C

$\frac{3}{2} (cos 2 0^{\circ+ 1})$

D

$\frac{3}{4} (cos 2 0^{\circ} + 1)$

Solution:

Correct answer is (a) $\frac{3}{4}$