The answer is either c or d. I would go with answer c though. sorry if it is wrong
Answer:
See below
Step-by-step explanation:
Here we need to prove that ,

Imagine a right angled triangle with one of its acute angle as
.
- The side opposite to this angle will be perpendicular .
- Also we know that ,


And by Pythagoras theorem ,

Where the symbols have their usual meaning.
Now , taking LHS ,

- Substituting the respective values,





Since LHS = RHS ,
Hence Proved !
I hope this helps.
4pi/2pi = x/360
use a proportion
2 radians equals 360 degrees
x = 720 degrees