Point b has coordinates (3,-4) and lies on the circle whose equation is x^2 + y^2= 25. if angle is drawn in a standard position with its terminal ray extending through point b, what is the sine of the angle?

Point B has coordinates (3,-4) and lies on the circle. Draw the perpendiculars from point B to the x-axis and y-axis. Denote the points of intersection with x-axis A and with y-axis C. Consider the right triangle ABO (O is the origin), by tha conditions data: AB=4 and AO=3, then by Pythagorean theorem:

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{Note, that BO is a radius of circle and it wasn't necessarily to use Pythagorean theorem to find BO}
The sine of the angle BOA is


Since point B is placed in the IV quadrant, the sine of the angle that is  drawn in a standard position with its terminal ray will be


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