Why is a thin prism always at minimum deviation?

[Misr]

1.the angles of thin prism are very small ,that's why the prism is always in the position of minimum deviation angle.
I don't understand this statement at all!how to prove this?

the deviation angle in a thin prism depends upon the refractive index but It doesn't depend upon the angle of incidence because the prism is always in the position of minimun deviation angle.

I don't understand this either.
Thanks in advance

 

[Misr]

am I using the right word "thin prism"?