If is the angle of deflection of a simple curve of radius R, the length of the curve is :

• A. <img src="/_files/images/civil-engineering/surveying/63-3.186-1.png">
• B. <img src="/_files/images/civil-engineering/surveying/63-3.186-2.png">
• C. <img src="/_files/images/civil-engineering/surveying/63-3.186-3.png">
• D. <img src="/_files/images/civil-engineering/surveying/63-3.186-4.png">
• E. .