 In this video, we'll find a general expression for calculating the slope of polar curves. Recall that the relationship between rectangular and polar coordinates is x equals r cosine theta and y equals r sine theta. And similar to the methods we used to find an expression for dy dx in parametric equations, using the chain rule on implicitly defined functions, we'll find dy dx by differentiating with respect to theta. So we have dy dx is equal to dy d theta over dx d theta. So another way of expressing this is d d theta of r sine of theta over d d theta of r cosine of theta. Now since r is a function of theta as well, we need to employ the use of product rule in both the numerator and the denominator. So dy dx is equal to dr d theta sine of theta plus r times the derivative of sine, which is cosine of theta, divided by dr d theta times cosine of theta plus r times the derivative of cosine, which is negative sine of theta. So cleaning this up, we have dr d theta times sine of theta plus r cosine of theta divided by dr d theta cosine of theta minus r times sine of theta.