so if sin and cosine are both ratios applied to different degrees (yes tan is too) the is the reason there different because of there applied sides of a triangle (SOH CAH TOA) for example sin30degrees is one half the sides in a 30-60-90 triangle and 1 2 and square 3 so since the sides that are one and two correspond to the opposite and hypotenuse how would you apply that to cosine?
I'm not sure I understand your question exactly, but this might help explain what sin and cosine are better: https://www.mathsisfun.com/geometry/unit-circle.html
Taking the sin or cosine of an angle will tell you the length one of the legs in a right triangle if the hypotenuse is one. The sin tells you the length of the "vertical" leg. Cosine tells you the length of the "horizontal" leg. (I put it in quotes because the triangle can be oriented differently.)