Question

If $6,10,14$ are the sides of a triangle then its obtuse angle is

• A. ${110}^0$
• B. ${120}^0$
• C. ${135}^0$
• D. ${115}^0$

Answer 1

The correct option is B ${120}^0$

$\cos \theta =\frac{6^2+{10}^2-{14}^2}{2\times 6\times 10}$

$=\frac{36+100-196}{120}$

$=\frac{-60}{120}$

$\cos \theta =-\frac{1}{2}$

$\theta ={120}^0$