Can you walk step by step how to do this asignment

First of all you have to know the definition of the cosine of an angle. ==> When the angle is in a right triangle, its cosine is (adjacent side) divided by (hypotenuse). NOW, draw a right triangle and sit down at one of the acute angles. On one side of you is the hypotenuse , and on the other side of you is the side adjacent to your angle. Their quotient is the cosine of your angle. Now, don't let the length of the hypotenuse change, but slowly start making your angle smaller, and watch what's happening to the right triangle. As you slowly close your angle, the side way over in the distance, the one that doesn't touch you, gets shorter and shorter. But the side next to you ... the adjacent side, gets longer and longer as it heads for the far end of the hypotenuse. When your angle finally closes down all the way and becomes 0 degrees, the adjacent side will lay right down on top of the hypotenuse, their ends will match, and their lengths will be equal ! Their ratio will be (the length) / (the length) and that's ' 1 '. The cosine of zero degrees is ' 1 '.