comput angl distanc equival given point conveni method help caller coordin form pass us link set displac vector param point desir target point arrai integ contain angl distanc comput vector point point point anchor anchor posit distanc anchor distanc point angl path slope slope offset slope slope anchor point swap path slope math pi path slope math pi angl offset slope path slope math pi angl offset slope path slope math pi result angl distanc result 