The fraction -4/3 can be written either as -4/3 or 4/-3.
tan is defined to be opposite divided by adjacent or, when graphed, as y / x.
If you write the fraction as -4/3, then the y-value (opposite) is -4 and the x-value (adjacent) is 3. This point is in Quadrant IV. Using the Pytagorean Theorem, the hypotenuse becomes 5. To find the sin, use the formula for sin, which is opposite over hypotenuse: sin(x) = -4/5.
If you write the fraction as 4/-3, the y-value is 4 and the x-value is -3, placing the angle in Quadrant II. The hypotenuse is again 5 and the sin becomes 4/5.
So, there are two possible answers.