Trigonometry Lecture Notes, Section 2.1

Note that the angle in the triangle at the bottom right is a right angle. Solution: Since we are given the angle and the hypotenuse, and are asked to find the side adjacent to the 42° angle, we can use the cosine ratio since it is stated in terms of these three values. Example 5: For the figure below, find the length of the hypotenuse. ................
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