[Dignan]

Originally Posted by Pisces

Asin, arcsin, sin with superscript -1 aka inv(erse) sine, all means the same function. It calculates an angle that corresponds with the slope of a vertical edge divided by the length of the sloping side (hypotenusa) in a right angled triangle. Though it can also be used with triangles that have no right angle (90 degrees) in them. The 'slope' must have a a value between -1 and 1, or else the angle cannot be calculated. No butts, no ifs, it can't!

In everyday household uses, the sine/cosine/tangent functions are calculated on degrees. As such the reverse kind of function: asin/acos/atan result in degrees. But most scientific calculators also have an option make them use angles in radians. A radian is the angle made when you wrap the radius of a circle around the circumference. Radians are a big thing in engineering and science. It's 57.29577951 degrees, or 180 degrees divided by Pi. 2 Pi radians make a full circle. On Casio calculators there should be a small 3 character abreviation in the top of the display: deg for degrees, rad for radians and gra for gradians. Gradians are a big thing in surveying.

To test your calculator for degree or radian mode: 0.707 asin should result in near 45 degrees, or 0.785398163 radians (=Pi/4), or 50 gradians (90 degrees angle is 100 gradians. The French trying to be funny there.)

So that could be the cause for unexpected results from the formula. Or the order of precedence in arithmetic: multiplication/division precedes adding/subtracting.

<-- is my face right now. I think I am beginning to understand what you are saying. I'm going to re-read this later and try to digest. Thanks for the explanation. So what I've done is plug this formula by Dorjun into an app called MagiCALc. It's a scientific calculator for the iphone. Here's what I've got.

Lead Angle = asin (V sin A / (V ^ 2 + T ^ 2 - 2VT cos A) ^ 1/2)
V= Target speed
T= Torpedo Speed
A= Track angle/Intercept angle.

The program automatically recognizes my variables and asks for input. When I input the following values for each as a test...

V(Target speed) = 9
T (Torp speed) = 30
A (Intercept angle) = 75

...it spits out (= -0.11)
I take this to mean an 11 degree lead angle. Is that how I should be doing this?

I tried it with a different lead angle variable again to be sure.
V(Target speed) = 9
T (Torp speed) = 30
A (Intercept angle) = 135

and it spit out (=0.02). or a 2 degree lead angle
That doesn't seem right to me. Can anyone see what I've done wrong here? Is my formula off? Do I need to make the calculator see my output "Lead Angle" as an angle and not a straight number value or something?

Pisces, thanks again for the trig refresher. While I love playing this game, this has reminded me why I was a "social science" person.