4 A particle is projected from horizontal ground with speed \(u \mathrm {~m} \mathrm {~s} ^ { - 1 }\) at an angle of \(\theta ^ { \circ }\) above the horizontal. The greatest height reached by the particle is 10 m and the particle hits the ground at a distance of 40 m from the point of projection. In either order,

1. find the values of \(u\) and \(\theta\),
2. find the equation of the trajectory, in the form \(y = a x - b x ^ { 2 }\), where \(x \mathrm {~m}\) and \(y \mathrm {~m}\) are the horizontal and vertical displacements of the particle from the point of projection.