From angle, sum property we know that sum of internal angles of a triangle is equal to 180°.

Considering it to be in A.P . let us assume first angle to be ‘a’ and smallest and now according to the question, the third and the largest is 5a . Now , let the second angle be equal to a+d , where ‘d’ is the common difference term of an AP. Using the properties of an AP , we get that , [(a+d) – (a)] = [5a - (a +d)]

[Property used: If X Y Z are in AP then Y – X = Z – Y ]

This gives , d = 4a -d ------ (1)

Also , a + (4a-d) + a + 5a = 180

11a - d = 180 --------- (2)

From 1 , d = 2a .

putting this in 2 .

a = 20 °.

d = 40°

So angles respectively will be 20 ° , 60° and 100°. Now these can be converted into radians by multiplying them by 0.0174.

Good Luck