I want to derive some physics equations from other equations. a) How can I derive this formula: R=Vo^2(sin(sα) / -a from these two equations: (1) x=(Vo cosα)t (2) y=(Vo sinα)t + 1/2at^2 Things I know - I think the way to do this is to isolate the variable t in equation (1) and substitute the t in equation (2). - Is the identity 2sin(theta) cos(theta)= sin(2theta) useful? -When the projectile returns to its original level y=0 Please help me understand how to do this. b) From equation y=yo + Vyo t + 1/2at^2 how can I show that: h= -1/2a(tf)^2 If I measure h and tf and recall that a=-g sin (theta) than this equation can be used to derive an equation for g in terms of tf, h and theta. Please help!