## Essential University Physics: Volume 1 (3rd Edition)

We first use the distance formula to find: $A = \sqrt{a^2 + (-b)^2} \\ A = \sqrt{a^2+b^2}$ We now are asked to find the phase constant. To do so, we set the derivative of the equation equal to zero: $0=-asin\omega t - b cos\omega t$ This becomes: $asin \phi = b cos \phi$ $atan \phi = b$ $\phi = tan^{-1}(\frac{b}{a})$