Hi, im making a wankel housing and the shape is an epitrochoid. How can I sketch it with an equation driven curve? I tried this but it doesn't work.

I got a sketch with e and R, that I got from here

I tried the following:

("e@Sketch1" (cos(3t)))+("R@Sketch1"(cos(t)))

("e@Sketch1" cos(3t))+("R@Sketch1"cos(t))

("e@Sketch1" (cos(3t))) + ("R@Sketch1"(cos(t)))

("e@Sketch1"(cos(3t))) + ("R@Sketch1"(cos(t)))

None of these work, as the equation shows up red. What do?