dear meritnation i need proof for first law of reflection of light. angle of incidence = angle of reflection​. plz answer needed fast

if you see  the picture below, you see that the incidence ray along with the reflected ray forms a 90⁰ angle.
​now, if you pass a normal , you see that both angles are 45⁰​ (i.e. the angle of incidence = the angle of  reflection)