Q3 of 24 Page 115

The angles of a triangle are in A. P. and the number of degrees in the least angles is to the number of degrees in the mean angle as 1 : 120. Find the angles in radians .

Given that angles are in AP, Let the three angles be,


(a – d), a and (a + d)


Such that, all three angles are in degrees and d>0 such that (a – d) is the least angle.


We know, By triangle sum property


(a – d) + a + (a + d) = 180


3a = 180


a = 60°


Also given, the number of degrees in the least angle is to the number of degrees in the mean angle is 1:120


Least angle = (a – d)





60 – d = 0.5


d = 59.5


Hence, angles are


(a – d) = 60 – 59.5 = 0.5°


a = 60°


(a + d) = 60 + 59.5 = 119.5°


Now, If θ is the angle in degree than the angle in radians is equal to



Hence, angles in radians are


Angle 1:


Angle 2:


Angle 3:


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