(i) In addition to degree and radian, there is a third measurement of an angle is called the grade.

(ii) When a right angle is divided in to 100 equal parts, each part is defined as "grade".

(iii) The symbol used is ^g (i.e, g as an exponent).

(iv) Each grade is sub-divided into 100 minutes (denoted as 100').

(v) Each minute is sub-divided into 100 seconds(100").

(vi) i.e, 1 right angle(or 90°) = 100 grades = 100^g

(vii) 1^g = 100'

(vii) 1' = 100"

Relation between 3 measures of an angles

If D is measure in degrees in, G in grades and r in radians, then

Note:

While the symbols °, ^c and ^g are used to indicate angles in degrees, radians and grades respectively, if there is no symbol it is assumed the measure of an angle is in radians.

• i.e, 90° = 90 degrees
• 90^c = 90 radians
• 90^g = 90 grades
• 90 ⇒ 90 radians

How many grades constitute a circle ?

• A circle has 4 quadrants, each with 90°
• Therefore a circle consists of 4 right angles.
• Since, each right angle is equal to 100 grades, a circle consists of 400 grades(400^g).