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Write the following function in terms of its cofunction. Assume that all angles in which an unknown appears are acute angles. sin (θ + 25°) (Simplify your answer. Do not include the degree symbol in your answer.)

Write the following function in terms of its cofunction. Assume that all angles in which…

Answer

The correct answer is: $\cos(65-\theta)$

Explanation

We use the cofunction identity for sine and cosine (angles in degrees):
$\sin x=\cos(90-x)$.

Steps:

  1. Let $x=\theta+25$. Apply the identity:

$$\sin(\theta+25)=\cos(90-(\theta+25))$$

  1. Simplify inside the cosine:

$$\cos(90-(\theta+25))=\cos(90-\theta-25)=\cos(65-\theta)$$

Therefore $\sin(\theta+25)=\cos(65-\theta)$. (As a check, using the evenness of cosine one may also write $\cos(65-\theta)=\cos(\theta-65)$, so both forms are equivalent.)

Summary: By the cofunction identity $\sin x=\cos(90-x)$ and direct substitution $x=\theta+25$, the expression simplifies to $\cos(65-\theta)$ (degrees implied; the final answer omits the degree symbol as requested).