To find sinΘ, we can draw the triangle dropping down to the x-axis with the red line as the hypotenuse (see the picture attached).
We know that sine is opposite/hypotenuse.
Given the coordinates of the point, we know that we have to go over 7/25 on the x-axis, and up 24/25 on the y-axis, which gives us the sides of the triangle. Now that we have the sides, we can set up an equation:
sinΘ=opposite/hypotenuse
sinΘ=(24/25)/1
sinΘ=24/25