Shortcut Trick
If the angles of a triangle are in an Arithmetic Progression (i.e., one angle is the average of the other two), the middle angle is always π/3 (or 60°).
Checking the given options, only the first set contains π/3 and sums to π radians.
Sum = π/6 + π/3 + π/2 = π.
Average of π/6 and π/2 = (π/6 + π/2) ÷ 2 = (4π/6) ÷ 2 = π/3.
∴ The correct answer is π/6, π/3, π/2.
Alternate Method
Given:
One angle of a triangle is the arithmetic average of the other two angles.
Formula Used:
Sum of interior angles in a triangle = π radians.
Average = (Sum of values) ÷ Number of values
A
B
C
π/6
π/3
π/2
Right-Angled Triangle with Angles in A.P.
Calculations:
⇒ Let the three angles of the triangle be A, B, and C.
⇒ According to the given condition, let B be the average of A and C: B = (A + C) ÷ 2
⇒ Multiplying by 2, we get: 2B = A + C
⇒ We know the sum property of triangles: A + B + C = π
⇒ Substituting A + C = 2B in the sum equation:
⇒ B + (A + C) = π
⇒ B + 2B = π
⇒ 3B = π → B = π/3
⇒ Since B = π/3, the remaining sum is A + C = π − π/3 = 2π/3
⇒ Checking the first set of angles from the options: π/6, π/3, π/2
⇒ Here, the middle angle is π/3. Sum of the other two angles = π/6 + π/2 = π/6 + 3π/6 = 4π/6 = 2π/3.
⇒ The first set identically matches all our derived geometric conditions.
∴ The correct answer is π/6, π/3, π/2.
Additional Information
Arithmetic Progression of Angles
When the angles of a triangle are in an Arithmetic Progression (A.P.), the middle angle is always exactly 60° (or π/3 radians), unconditionally regardless of what the other two adjacent angles are.
Sum of Angles Property
The sum of interior angles in any Euclidean planar triangle is strictly equal to 180° (which is algebraically equivalent to π radians). Universal formula: A + B + C = π.
Radian and Degree Conversion
To convert a measurement from radians to degrees, we multiply the given radian value by 180°/π. For example, π/6 × (180°/π) = 30° and π/2 × (180°/π) = 90°.