1. SOH CAH TOA tells you the tangent is the ratio of the Opposite side to the Adjacent side, that is, 4/3. (This correct answer is not among your choices.)
2. The mnemonic SOH CAH TOA can be helpful here. It tells you
... Sin = Opposite/Hypotenuse
... Cos = Adjacent/Hypotenuse
... Tan = Opposite/Adjacent
3. Reference the ratios listed above (for the second problem). You see that sin(α) = cos(90°-α). That is, the sine of an angle is the cosine of its complement and vice versa. The appropriate choice is
... D. 19/20