arcsin function

[leif]

How do I do the formula

B= 180-arcsin((Ri-Cl/Re)

[kedaman]

Arcsin(X) = Atn(X / Sqr(-X * X + 1))

[[Digital-X-Treme]]

Please post your question in one forum only. I replied to your other thread here... http://www.vbforums.com/showthread.p...threadid=98363

Laterz

[Guv]

VB has no inverse trig functions other than Atn (inverse Tangent). You can use so called derived functions as per a prior post.

In almost every practical situation, you can use the inverse tangent directly.

Sine and cosine are the ratios between the hypotenuse and a side of a right triangle. Tangent is the ratio of two sides of a right triangle.

Sine = OppositeSide / Hypotenuse
Cosine = AdjacentSide / Hypotenuse
Tangent = OppositeSide / AdjacentSide

If you keep the above ratios in mind you can work out how to use inverse tangent for inverse sine or inverse cosine.

If you have XY-coordinates, the following are valid.

Sine = Y / R
Cosine = X / R
Tangent = Y / X

Where R is the distance of the point from the origin.
R = Squareroot( X^2 + Y^2)

[kedaman]

Digital-X-Treme, leif
Try not to waste performance by doing as few calculations as possible

B = 180- Atn((Ri-Cl/Re) / Sqr(-(Ri-Cl/Re) * (Ri-Cl/Re) + 1))

X=Ri-Cl/Re
B = 180- Atn(X / Sqr(-X * X + 1))
Guv
And I remeber you wondered why -X * X + 1 and not 1 - X * X

The answer is that X * X is evaluated first, if this operations is to take n cpu instructions the whole expression will take n+2; the negation of the result followed by incremention. The later expression would require either an extra register or be stored temporarily in RAM, while the register would be filled with 1 and then substract X * X from it which takes at least n+3, and the additional register.