If the angle m∠EDH = 18° then m∠EDF = 72°
If a = 9 and c = 41, then the value of b = 40.
Since we have that DF is perpendicular to GE and GE is perpendicular to EH, then DHEG is a rectangle which implies that the angle m∠GDH is equal to 90°
Thus if m∠EDH = 18° then;
m∠EDF = 90 - 18
m∠EDF = 72°
Also, given that DF is perpendicular to GE, then the triangle ∆DGE is a right triangle and the Pythagoras rule can be used to find the value of b as follows:
a² + b² = c²
9² + b² = 41²
81 + b² = 1681
b² = 1681 - 81 {collect like terms}
b² = 1600
b = √1600 {take square root of both sides}
b = 40.
Therefore, the measure of the angle m∠EDF is 72°, and the value of b is 40 derived using the Pythagoras rule.