Using Pythagorean theorem, we can justify our answer. if c^2 = a^2 + b^2 then triangle is right one, if c^2 > a^2 + b^2 then triangle is obtuse and if c^2 < a^2 + b^2 then triangle is acute triangle.
Here a=8, b=11 and c=16 Put these values in the equation 16^2 = 8 ^2 + 11^2 256 = 64 +121 256> 185 So here c^2 > a^2 + b^2 Which means triangle is obtuse triangle.