I'm stuck on how to approach these 2 problems - any hints would be much appreciated!

1.

A body is projected form a point O on horizontal ground with velocity of 70m/s. It passes through a point P, which is 45m above the ground and 50m from O horizontally. Find the tangents of the two possible angles of elevation of the projected body. Find also the gradients at P of the two paths.

2.

The maximum range of a certain gun on a horizontal plane is R. Find the two possible angles at which the gun can be fired to give a range of 1/2R. If T1 and T2 are corresponding times of flight, find T1:T2.