Plotting triangles based on a single point with distance and angle.

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I'm tasked with creating an arrowhead within a pdf program.

I have a single point with at $x=5.6$, $y=4$ this would be point A of my triangle I want to make the sides equal at $90$ degrees angles and a distance of around $.1$. How would I go about doing this, or is this even possible? Im pretty rusty on trig.

Thank you

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Use vectors or complex numbers. In this case, they are essentially the same.

If a point is at $(x, y)$, to rotate it about the origin by an angle $t$, do a multiplication (switching between points and complex numbers)

$\begin{array}\\ (x+iy)e^{it} &= (x+iy)(\cos t+i \sin t)\\ &=(x, y)(\cos t, \sin t)\\ &=(x\cos t-y\sin t)+i(x\sin t+y \cos t)\\ &=(x\cos t-y\sin t, x\sin t+y \cos t)\\ \end{array} $

This is all standard stuff which you will have to get familiar with to do the things you want to do.