Question

4. is it right to say cos (60°+ 30°)=
cos 60°cos 30° - sin 60° sin 30°?​

Answer 1

Answer:

Hey mate , it is right.

Step-by-step explanation:

because it suits on the formula that

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

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Answer 2

Answer:

We know that,

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

= $\frac{1}{2}$ x $\frac{\sqrt{3} }{2}$ - $\frac{\sqrt{3} }{2}$ x $\frac{1}{2}$

= $\frac{\sqrt{3} }{2} - \frac{\sqrt{3} }{2}$ = 0

⇒ cos (60° + 30°)

We know that,

= cos (A + B) = cos (60 + 30)

= cos 90°

⇒ 0

Hence, Yes it is right to say that

cos(60° + 30°) = cos 60°cos 30° − sin 60° sin 30°

⇒ LHS = RHS