Answer: \( \cos(65^\circ - \theta) \)
Explanation: The problem involves expressing the sine function in terms of its cofunction, cosine. The cofunction identity for sine and cosine states that \(\sin(90^\circ - x) = \cos(x)\). We need to express \(\sin(\theta + 25^\circ)\) using this identity.
Steps:
- Identify the Cofunction Identity:
- The cofunction identity for sine is \(\sin(90^\circ - x) = \cos(x)\).
- Rewrite the Expression:
- We have \(\sin(\theta + 25^\circ)\).
- To use the cofunction identity, we need to express this in the form \(\sin(90^\circ - x)\).
- Set up the Equation:
- Let \(x = 90^\circ - (\theta + 25^\circ)\).
- Simplify:
- Apply the Cofunction Identity:
- Using \(\sin(90^\circ - x) = \cos(x)\), we have:
Therefore, \(\sin(\theta + 25^\circ)\) is expressed as \(\cos(65^\circ - \theta)\).