The form of - 10 is 2K pie + a (0 ≤ a < 2K pie, K is an integer) It's - 10, not - 10 degrees!

The form of - 10 is 2K pie + a (0 ≤ a < 2K pie, K is an integer) It's - 10, not - 10 degrees!

There is a wrong arc angle upstairs, so it can't be mixed up
-10≈-3.185π=-4π+0.815π
∴-10≈-4π+0.815π(k=-2)