Mathematics

The key to solving $\sin x = 0.218$ is understanding that sine is not one-to-one over a full period—for any positive value less than 1, there are two angles in $[0, 2\pi]$ where sine equals that value. Use your calculator's inverse sine to find the acute angle in the first quadrant, then use the symmetry of the sine curve to locate the second solution in the second quadrant.

The key to solving $\sin x = 0.218$ is understanding that sine is not one-to-one over a full period—for any positive value less than 1, there are two angles in $[0, 2\pi]$ where sine equals that value. Use your calculator's inverse sine to find the acute angle in the first quadrant, then use the symmetry of the sine curve to locate the second solution in the second quadrant.