Hi riya,

 

We can always make the diagram this way

 

Now, here b is not the maximum height attained.

 

Look,

 

Components of velocity are ucosk and usink where k is angle f projection.  

 

Let us consider the point where it clears the wall. So,

 

 b = (usink)t - 0.5*g*t²       

 

and , at the same point

 

a = (ucosk)t

 

Put value of t from this eq. to previous one.

 

We get,

 

b = a*tank - 0.5ga²/u²cos²k  

 

 

b =( au²sinkcosk - 0.5ga² )/u²cos²k

   =( 0.5au²sin2k - 0.5ga² )/u²cos²k

 

Now,

 

as c is range,

so,

 

c = u²sin2k / g

 

Substitute value of sin2k from here in the previous equation and get the answer. In that equation you will get value of sec²k, convert it to 1 + tan²k and manipulate to get the answr.

 

 

 

Hope u got it !!!!!!!

 

Do tell me in case of problems.