Help needed with sin, cos & co...

[artmusicstudio]

hi there,
so i stick in place with a math-problem:

let us assume, i have

two lines in a traingle defined with
a1
b1

i can count the angle by

@mainangle_l = Math;;atan(a1/b1).radians

puts also gives me the right angle in the console (compared with the drawing = check)

in the next step i have to calculate another triangle, same angle, but have values
@mainangle_l
c2

BUT

a2 = c2 * Math.sin(@mainangle_l))

does not give me the right value for a2

i tried different variations of the syntax, but no way to get it.

obviously i define the Math-function in a wrong way. but in the api, i canot find examples.

can anybody help fo rgeneral understanding of trigon. functions??

thanx a lot!!!

stan

---

[TIG]

The atan only works for a right-angled triangle.
Because all 3 angles always add up to 180 degrees then:

a2 = 180.degrees - (Math::atan(a1/b1))

The angle a2 is in radians

a2.radians

gives it in degrees...

I think you are jumbling up radians and degrees [again]

You can use other 'Sine Rule' formulas to find relationships between the enclosed angles and their opposing sides etc, when there is NO right-angle in the three angles - like:

a/sinA = b/sinB = c/sinC = d
Where ' d' is the diameter of the enclosing circle that passes through the 3 vertices
substitute the desired lengths and the real sine values for the angles [using radians/degrees appropriately]...

Rearrange the formulas to get any value... e.g.

a = sinA*b/sinB

or

A = asin(a*sinB/b)

Note too that the triangle's area is found using a*b*sinC/2
or similar permutations of the values...

[artmusicstudio]

hi tig,
great , good formulas for further studies.
my code works now, by the way.

just to precise my informations:

i understand, that "atan" only works for right-angled triangles (one angle = 90 degrees),
but: is the sum of angles not 180 degrees in all triangles?
so the criterium is the right angle, not the sum of 180 °, right ?

"jumbling up radians and degrees [again]" _:)
yes, i still sometimes mix it somehow, but i try to keep all calculaction in skp-origin
and only to display in the console in degrees. seems to work now! _

so thanx again, all your tips makes my learning much easier!

btw.: when a beta of the ruby is done and i made my tests, do you think, you and maybe somebody else , too, could check it on his machine?

i have lots of rubys in my sketchup, so the compatibility here is ok, but who knows...!!!

thanx stan