Answer:
sin θ = 4/5
Step-by-step explanation:
The Pythagorean theorem tells you the distance (h) from the origin to the terminal point:
h² = (-3)² +(4)² = 25
h = 5 . . . . . . . . take the square root
The mnemonic SOH CAH TOA reminds you ...
Sin = Opposite/Hypotenuse
For angles other than 1st-quadrant angles, it can sometimes be difficult to identify the relevant sides of the relevant triangle. If the angle were a 1st-quadrant angle, it would be clear that the side opposite the angle is the y-coordinate of the point on the terminal side. That remains the case for all angles. The hypotenuse is always the positive distance from the origin to the terminal point.
So, you have
sin θ = opposite/hypotenuse = 4/5
