How do i find the release angle of an object

This is what I know, The angle of releases changes the relationship between the horizontal and vertical components of projectile. The idea angle of release  is 45 degrees, assuming there is no air resistance and take off and landing points are the same height.

Explanation:

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.