Trigonometry
r=31cos2θr=\(\frac{31}{\cos^2\theta}\)r=cos2θ31
r=31sinθcos2θr=\(\frac{31\sin\theta}{\cos^2\theta}\)r=cos2θ31sinθ
r=31cosθsin2θr=\(\frac{31\cos\theta}{\sin^2\theta}\)r=sin2θ31cosθ
r=31sinθcosθr=\(\frac{31\sin\theta}{\cos\theta}\)r=cosθ31sinθ