vb.net - How to work out the X and Y coordinates of a moved pendulum -

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i trying make pendulum simulation in vb.net, move string of pendulum using:

e.graphics.drawline(pens.black, 270, 0, 270, lengthofstring)

and changing end coordinates rotate line around point (270, 0). end making isosceles triangle. know 2 equal lengths (lengthofstring). how work out lower (not (270, 0) x , y coordinate of rotated line.

i have tried work out with: pythagoras (to work out lower line's length) trig, after splitting triangle in half

if starting angle let φ, known then:

sinφ = x / lengthofstring cosφ = y / lengthofstring

the end points:

(270 - x, 0 + y), (270 + x, 0 + y)

enter image description here


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