Originally Posted by
HallsofIvy Corum, on this forum use "\", not "#". Also, the final "/MATH must be completely inclosed in [ ].
"[ math ] \theta [ /math ] (without the spaces) gives $\displaystyle \theta$.
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Dynamo, to rotate y= f(x) through angle $\displaystyle \theta$, around the origin, replace x with $\displaystyle x'= x cos(\theta)+ y sin(\theta)$ and y with $\displaystyle y= -x sin(\theta)+ y cos(\theta)$.
To rotate y= f(x) through angle $\displaystyle \theta$, about point [tex](x_0, y_0), first translate [tex](x_0, y_0) to the origin by subtracting $\displaystyle x_0$ from x and $\displaystyle y_0$ from y, then do the rotation, then translate back.
That is, replace x with $\displaystyle x'= (x- x_0)cos(\theta)+ (y- y_0)sin(\theta)+ x_0$ and replace y with $\displaystyle y'= -(x- x_0)sin(\theta)+ (y- y_0)cos(\theta)+ y_0$