The Wronskian & Variation of Parameters · Easy problem

Let $y_1,y_2$ be solutions of $y''+(\tan t)\,y'+e^{t}y=0$ on $-\dfrac{\pi}{2}<t<\dfrac{\pi}{2}$ with $W(y_1,y_2)(0)=3$. Find $W(y_1,y_2)\!\left(\dfrac{\pi}{3}\right)$.