15^ = - Vidyadip

MCQ

$\cos 15^{\circ}=$

✓
$\sqrt{\frac{1+\cos 30^{\circ}}{2}}$
B
$\sqrt{\frac{1-\cos 30^{\circ}}{2}}$
C
$\pm \sqrt{\frac{1+\cos 30^{\circ}}{2}}$
D
$\pm \sqrt{\frac{1-\cos 30^{\circ}}{2}}$

✓

Answer

Correct option: A.

$\sqrt{\frac{1+\cos 30^{\circ}}{2}}$

(A)
$\cos 15^{\circ}=\sqrt{\frac{1+\cos \left(2 \times 15^{\circ}\right)}{2}}=\sqrt{\frac{1+\cos 30^{\circ}}{2}}$

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