Cos and Sin

[chenko]

Ok, ive already done my exams so i dont need to remember


now which one do I use to work out the oposite sides (cant remember what they are called) of a triangle when i only have the angle and the length of the hypothonuse?

  |\
  | \
  |  \
a |   \  h
  |_   \
  |_|__(\ 
      b

[chrisf]

opposite: a = h sin angle
adjacent: b = h cos angle

[chenko]

a = Cos(Angle) * h
b = Sin(Angle) * h

thats what i got and it returns negative numbers most of the time

[chrisf]

If (angle mod 360) > 180 then h * sin (angle) will be negative.
If (angle mod 360) > 90 and < 270 then h * cos (angle) will be negative.
(Assuming h is positive)

[chenko]

angle will always be greater than 0 and less than 90, it will NEVER be 0 or 90

h is ALWAYS positive.


what im trying to do is move one end of a line in a semi circle based on a perentage given to it ie. 25% is 45deg and as with a line you can specify the length or the angle i work the angle out from the percentage (percentage * 1.8)

i have attacted my form.... ignore all the lines (they were there for other purposes) end even the circle, except the red and blue lines

ive sorted the code to minus 90deg if it is over 90deg and mark in a varible (Acute_Angle) so that i know wether to add a (length on the X axis) to the postion of the center where the line meets its base line

if ya dont understand anything just ask


cheers

[chenko]

what the hell?!?!?!

Sin(30) returns : -0.988031624092862

its supposed to be 0.5 !!!

[chrisf]

All trig calculations must be done in radians (360 deg = 2 * Pi radians)

I've changed your form a little, is this what you wanted?

[chenko]

that sorta works

but if i put 0% it seams to start at 45deg and 100% is 135deg


thanks lots for that!

[chenko]

Originally posted by chenko
thanks lots for that!

sorry that sounded rude.


if i put -50% it is set at 0deg and 150% = 180deg..... ummmm

[chrisf]

now 0%-> 0 deg.
100%->180 deg.

Hope this helps.

It was odd before so the line pointed roughly towards the marks on the form.

[HarryW]

Haven't looked at the code but in case it's helpful, this function will convert from a percentage of 90 degrees to the equivalent in radians:

Function Percent2Radians(Percentage As Double) As Double
    '90 / 100 * pi / 180 = 0.015707963267948966192313216916398
    Percent2Radians = Percentage * 0.015707963267948966192313216916398
End Function

I'm not sure how accurate you can make that constant, round it down if it's too long.

[chenko]

well i can easily convert degrees to radians

thank you both anyways...

I spent 3 days figuring that out *ahem* time wasting *ahem*


thanks

si