Math help?

The lines OP, OQ, OR, OS and OT divide the regular pentagon PQRST into 5 congruent triangles, i.e.
ΔPOQ ≅ ΔQPR ≅ ΔROS ≅ ΔSOT ≅ ΔTOP
ie. ∠POQ = ∠QOR = ∠ROS = ∠ΔSOT = ∠ΔTOP

But ∠POQ + ∠QOR + ∠ROS + ∠ΔSOT + ∠ΔTOP = 360° (∠s at a pt.)
Hence, 5 ∠QOR = 360°
∠QOR = 72°

360/5 = 72 degrees

Since PQRST is regular, all the central angles

are equal, so each angle is 1/5 x 360 = 72º

(The radius is irrelevant)