1. The problem statement, all variables and given/known data A projectile is thrown on an inclination plane with incline angle phi with an inital velocity V0 on an angle theta. Find the range of the projectile; treat the hypotenuse of the inclined plane as the x-axis. For what value of initial velocity angle is the range maximum, and what is that range. 2. Relevant equations All 2D kinematics equations. 3. The attempt at a solution Firstly I used the equation y(t) and expressed flight time as 2Vy/-gy (g is negative itself, the minus in front of it makes it positive), from there I wrote t=(2V0*sintheta)/(-g*cosphi). Then I plugged that into the equation for range which is D=Vx*t+1/2gx*t^2 where gx is the x-axis component of g. By simplifying the expression I obtained D=(2V0^2*sintheta*(-costheta*cosphi+sintheta*sinphi))/(g*(cosphi)^2). Now everything is correct except the bolded part which should be costheta*sin(theta-phi). Help please.