arc functions are the inverse functions of the trigonometric function. So, if we have an angle, for instance, 60°, we can input it to a sin, cos or tan function to get the results:
The arc functions, arcsin, arccos and arctan, is the other way around: we have a sin/cos/tan value and want the corresponding angle, so:
9) To find the missing angles, e can use arc functions, the inverse functions of the trigonometric functions.
We have the opposite leg of the angle and the hypotenuse, so we have:
10) We want the adjacent leg, given the angle and the opposite leg, so we use tangent:
11) Just like 9, we want an angle given its opposite leg and hypotenuse. So we use sine: