A square room has 3 mirrored walls of length L with one side missing. A laser is fired from the center of the open side of the room with an angle of incidence, I, toward the wall on the right. If the reflected beam is to hit a target on the back wall .80 of L from the right wall, what must be the angle of incidence be?
Y1 = lower right wall
tan i = Y1/(L/2)
Y1 = (L/2) tan i
Y2 = upper right wall = L-Y1 = L - (L/2) tan i
or
Y2 = L (1 - .5 tan i)
now in upper triangle
tan i = L(1 - .5 tan i)/.8 L
or
tan i = 1.25 - .625 tan i
1.625 tan i = 1.25
tan i etc