Prove that
aplpha+beta+gamma=90°
Plz show step i dont
That's "dying"
and I have no ideas what your three angles are supposed to be. If they are the angles of a triangle, just draw a line at one vertex, parallel to the opposite base.
Next, recall that alternate interior angles between parallel lines are congruent.
The three angles at your vertex and line add to 180 degrees. So, that means the three angles of the triangle do as well.