1. The problem is to understand when to use sine, cosine, or tangent in a right triangle. 2. The key is to remember the definitions of sine, cosine, and tangent based on the angle and the sides of the triangle: - Sine ($\sin$) of an angle = Opposite side / Hypotenuse - Cosine ($\cos$) of an angle = Adjacent side / Hypotenuse - Tangent ($\tan$) of an angle = Opposite side / Adjacent side 3. To decide which to use, identify the angle you are working with and the sides you know or want to find: - If you know or want the ratio involving the hypotenuse and the opposite side, use sine. - If you know or want the ratio involving the hypotenuse and the adjacent side, use cosine. - If you know or want the ratio involving the opposite and adjacent sides, use tangent. 4. In your case, you used cosine and got 60. This means you used the ratio of the adjacent side over the hypotenuse for the angle. 5. Always label the triangle sides relative to the angle you are considering to choose the correct function. 6. Summary: Use $\sin$ for opposite/hypotenuse, $\cos$ for adjacent/hypotenuse, and $\tan$ for opposite/adjacent.