help me plsss, this is worth 30 points!! can someone pls help even if u can only give a few answers it would be helpful.

What is the length x of the side of the triangle below? (hint: use the cosine function)

Which word expression describes how much to calculate pressure

Aparticle of mass m is placed in a one-dimensional box of length l. the box is so small that the particle’s motion is relativistic, so that e p2/2m is not valid. (a) derive an expression for the energy levels of the particle using the relativistic energy–momentum relation and the quantization of momentum that derives from connement. (b) if the particle is an electron in a box of length l 1.00 1012 m, nd its lowest possible kinetic energy. by what percent is the nonrelativistic formula for the energy in error?