darn trigonometry...

ok, I know how to use Sin, Cos, etc to find the length of a side of a triangle, but what's the command to find the angle of a corner? (if there isn't one, how???):mad:

What infomation do you have, e.g. length of sides, angles of other positions?

P.S. when replying, if u can, discribe what you know as if the triangle went through the points A, B and C

e.g. AB=3

angle A = 40^o

In a right triangle, find the measure of one of the non-90 degree angles like this:

tan(angle) = opposite side / adjacent side

or

angle = arctan(opposite side / adjacent side)

You can use arcsin and arccos in a similar fashion (if you know the measure of the hypotenuse).

angle = arcsin(opposite / hypotenuse)
angle = arccos(adjacent / hypotenuse)

Well, you just remember that forumla thingy.

A² + B² = C²

(The squared length of one side is equal to the square of the sum of the other 2 sides) :)

I know a² + b² = c² and I know how to find the length, but I want the angle, I have the length of all 3 sides, and no angles.

edit: arctan/sin/cos causes error, function not defined

yes its a right triangle (thats the one with a 90 degree right? (french school)

Sorry, I didnt notice

is the triangle right-angled?

I know a² + b² = c² and I know how to find the length, but I want the angle, I have the length of all 3 sides, and no angles.

edit: arctan/sin/cos causes error, function not defined

yes its a right triangle (thats the one with a 90 degree right? (french school)


__________________

SOHCAHTOA

What this means is

SOA

Take the sin of the opposite side over the adjacent side.

CAH

Take the cos of the adjacent side over the hypoteneuse

TOA

Take the tan of the opposite side over the adjacent side

This only works for right angled triangles.

There is another formula which I don't know at the moment for other types of triangles.

Atn(((a²+b² - c²)/2ab) / Sqr(-((a²+b² - c²)/2ab) * ((a²+b² - c²)/2ab) + 1))

This finds the angle where lines A and B meet, i hope :)

I already know SOHCAHTOA, I know a² + b² = c² I can find angle on a calculator, I just need to know the function's name!!!! last 3 I got (acrsin, arc cos, arctan) made errors.

Quote:

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Originally posted by ae_jester
There is another formula which I don't know at the moment for other types of triangles.

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The cosine rule

c²=a²+b²-2ab*sin(c)

Quote:

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Originally posted by alkatran
I already know SOHCAHTOA, I know a² + b² = c² I can find angle on a calculator, I just need to know the function's name!!!! last 3 I got (acrsin, arc cos, arctan) made errors.

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You need to create them yourself, hold on...

Try the law of Sines.

Lets hope this is what you want

Secant Sec(X) = 1 / Cos(X)
Cosecant Cosec(X) = 1 / Sin(X)
Cotangent Cotan(X) = 1 / Tan(X)
Inverse Sine Arcsin(X) = Atn(X / Sqr(-X * X + 1))
Inverse Cosine Arccos(X) = Atn(-X / Sqr(-X * X + 1)) + 2 * Atn(1)
Inverse Secant Arcsec(X) = 2 * Atn(1) – Atn(Sgn(X) / Sqr(X * X – 1))
Inverse Cosecant Arccosec(X) = Atn(Sgn(X) / Sqr(X * X – 1))
Inverse Cotangent Arccotan(X) = 2 * Atn(1) - Atn(X)
Hyperbolic Sine HSin(X) = (Exp(X) – Exp(-X)) / 2
Hyperbolic Cosine HCos(X) = (Exp(X) + Exp(-X)) / 2
Hyperbolic Tangent HTan(X) = (Exp(X) – Exp(-X)) / (Exp(X) + Exp(-X))
Hyperbolic Secant HSec(X) = 2 / (Exp(X) + Exp(-X))
Hyperbolic Cosecant HCosec(X) = 2 / (Exp(X) – Exp(-X))
Hyperbolic Cotangent HCotan(X) = (Exp(X) + Exp(-X)) / (Exp(X) – Exp(-X))
Inverse Hyperbolic Sine HArcsin(X) = Log(X + Sqr(X * X + 1))
Inverse Hyperbolic Cosine HArccos(X) = Log(X + Sqr(X * X – 1))
Inverse Hyperbolic Tangent HArctan(X) = Log((1 + X) / (1 – X)) / 2
Inverse Hyperbolic Secant HArcsec(X) = Log((Sqr(-X * X + 1) + 1) / X)
Inverse Hyperbolic Cosecant HArccosec(X) = Log((Sgn(X) * Sqr(X * X + 1) + 1) / X)
Inverse Hyperbolic Cotangent HArccotan(X) = Log((X + 1) / (X – 1)) / 2
Logarithm to base N LogN(X) = Log(X) / Log(N)

A/sin(a) = B/sin(b) = C/sin(c)

I've tried alot of it, error... error.. to make it clearer... maybe.. I want to unsin a sin... so if sin(a) = 3 then unsin(3) = a.

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

VB Code:

Private Function ArcSin(X)
    Atn(X / Sqr(-X * X + 1))
End Function