The angles of a quadrilateral are in A.P., and the greatest angle is 1200. Express the angles in radians.
Let the angles of quadrilateral be (a – 3d) °, (a – d) °, (a + d) ° and (a + 3d) °.
We know that the sum of angles of a quadrilateral is 360°.
⇒ a – 3d + a – d + a + d + a + 3d = 360°
⇒ 4a = 360°
∴ a = 90°
Given the greatest angle = 120°
⇒ a + 3d = 120°
⇒ 90° + 3d = 120°
⇒ 3d = 120° - 90°
⇒ 3d = 30°
⇒ d = 10°
Hence, the angles are:
⇒ (a – 3d) ° = 90° - 30° = 60°
⇒ (a – d) ° = 90° - 10° = 80°
⇒ (a + d) ° = 90° + 10° = 100°
⇒ (a + 3d) ° = 120°
Angles of quadrilateral in radians: