Question

write the expression as the sine or cosine of an angle.
cos 94° cos 18° + sin 94° sin 18°
hint: sin(a ± b) = sin a cos b ± cos a sin b
cos(a ± b) = cos a cos b ∓ sin a sin b

Explanation:

Step1: Recall the cosine of difference formula

The formula is $\cos(A - B)=\cos A\cos B+\sin A\sin B$.

Step2: Identify $A$ and $B$

Here, $A = 94^{\circ}$ and $B=18^{\circ}$.

Step3: Apply the formula

Substitute $A$ and $B$ into the formula: $\cos(94^{\circ}-18^{\circ})$.

Step4: Calculate the angle

$94^{\circ}-18^{\circ}=76^{\circ}$.

Answer:

$\cos76^{\circ}$