Arcsine

[astronomer]

I'm having rouble getting the ASIN function to work. By the way, thanks to those who helped me with my last problem- Arctangent.

[BillSoo]

To my knowledge, there is no built in asin function so you have to write your own....most likely by using atan as a starting point.

You know that Sin(theta) = opposite/hypotenuse so that ASin(opposite/hypotenuse) = theta.

Given 2 sides of a right angle triangle, we can determine the 3rd side using pythagoros so...

h*h = o*o + a*a

a * a = h * h - o * o

a = sqr(h*h - o*o)

Knowing the length of the adjacent side and the opposite side, we can now use the atan function to calculate the angle.

[Deadalus]

There is a section 'Derived Math Functions' in the VB help. For this one it gives: Arcsin(X) = Atn(X / Sqr(-X * X + 1)).