Originally Posted by

**markosheehan** a particle is projected up an inclined plane with initial velocity u m/s .the line of projection makes angle a with the horizontal and the inclined plane makes angle b with the horizontal. show that the range is a maximum when a=45°+b/2

so far I got the time of flight =$\displaystyle 2usinb-a/(gcosa) $

and i have gotten the range =$\displaystyle [cos(b-a) -{(sina*sinb-a)/cosa} ] [(2u^2sinb-a)/gcosa] $

from here i cant see how to maximise this using differentiation or trigonometry.