1.

One of the angles of a triangle is 1/2 radian and the other is 99°. What is the third angle in radian measure? 1. \(\dfrac{9\pi - 10}{\pi}\)2. \(\dfrac{90\pi - 100}{7\pi}\)3. \(\dfrac{90\pi - 10}{\pi}\)4. None of the above

Answer» Correct Answer - Option 4 : None of the above

Concept:

The sum of all angles of a triangle is 180° = π 

Calculations:

Given, one of the angles of a triangle is 1/2 radian and the other is 99°.

⇒ \(\rm ∠ A = (\dfrac 1 2)^c\) and ∠B = 99° 

Convert the ∠B  into radians by multiplying by \(\rm \dfrac {π}{180^\circ}\).

⇒ \(∠ B = 99^\circ \times \dfrac {π}{180^\circ}\) = \(\dfrac {11π}{20}\)

As we know, the sum of all angles of a triangle is 180° = π

⇒ \(\rm ∠ A + ∠ B + ∠ C = π\)

⇒ \(\rm ∠ C = π - (∠ A + ∠ B)\)

⇒ \(\rm ∠ C = π - (\dfrac 12 + \dfrac{11π}{20})\)

⇒  \(\rm ∠ C = π - (\dfrac {10 + 11π}{20})\)

⇒  \(\rm ∠ C = \dfrac {9π -10}{20}\)

Hence, one of the angles of a triangle is 1/2 radian and the other is 99°, then the third angle in radian measure is \(\rm ∠ C = \dfrac {9π -10}{20}\)



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