The inverse function in trigonometry for the term 'arcsine' is a seven letter word. Arcsine is a mathematical function that is the inverse of the sine function. It is used to calculate the angle from the ratio of the opposite side and the hypotenuse of a right triangle. The arcsine of a number is the angle between the positive x-axis and the ray from the origin to the point on the unit circle with the given x-coordinate.