A few ways. you can enter it into a calculator for one, but the easiest way would be to reference a unit circle and look for an ordered pair where sin (the y value), is equal to -1/2
on a unit circle, the sin value is -1/2 at 7pi/6 and 11pi/6
because sin is the y value, it will additionally be in the quadrants III or IV based on the fact that (-1/2) as a sin value IS a negative and would have to be found in a quadrant in which sin is negative (the lower half of a coordinate plane, in this case)
Use the midsegment theorem
Well you would take the store credit and subtract that from the total so you would do 52.22-39.58 and you would have to spend $12.64
42.41 cubic meters
The volume of a cylinder is bh where b is the area of the base and h is the height of the cylinder. And since the area of a circle is pi r^2, we have this equation for the volume of a cylinder
V = pi*r^2*h
Now substitute, the known values for r and h, then calculate the result:
V = pi*r^2*h
V = 3.14159*3^2*1.5
V = 3.14159*9*1.5
V = 42.411465
V = 42.41
So the volume of the coal pile is 42.41 cubic meters.
