cos 73° cos 17° - sin 73° sin 17° का मान होगा (A) -1 (B) 0 (C) 1

Question

\(\cos 73^{\circ} \cos 17^{\circ}-\sin 73^{\circ} \sin 17^{\circ}\) का मान होगा

(A) -1

(B) 0

(C) 1

(D) \(\pm 1\)

Answer 1

Correct option is (B) 0  

As we know that,

cos (A + B) = cos A Cos B - sin A sin B

Here, \(A = 73^{\circ}\ \text{and} \ B = 17^{\circ}\) 

\(\cos (73^{\circ} + 17^{\circ}) = \cos 73^{\circ} \cos17^{\circ} - \sin 73^{\circ} \sin17^{\circ}\)   

\(\therefore\ cos(73^{\circ} +17^{\circ})\)  

\(= \cos 90^{\circ}\)

= 0