This figure better be a square, otherwise there is no answer.
The diagonals of a square intersect at right angles, so d = 90 degrees. That property comes from the rhombus.
Squares have equal sides and the opposite sides are parallel. The triangle containing c is isosceles. The lower right corner is a right angle. So c must equal 45 degrees since the angle on the lower left must equal 45 degrees as well
