They're all 30-60-90 triangles so you don't need law of cosines or anything like that. Solve given the variables, its easy. if you have opposite and the hypotenuse, put the sine of that angle equal to the opposite side value over the hypotenuse. If you have the adjacent side of the triangle, as well as the hypotenuse, then set the cosine of that angle equal to the adjacent side over the hypotenuse. If you have no hypotenuse, at you level, you ought to have the opposite side and the adjacent, so just set the tangent of that angle equal to the opposite side over the adjacent. Throw those into your calculator and it does all the work for you, little derivations necessary.