Determine whether a triangle with sides 12 cm, 14 cm and 18 cm is an acute, right or obtuse triangle.
Solution:
We choose the two shorter sides to be a and b and the longest side to be c. So a = 12, b = 14 and c = 18. a2 + b2 = 122 + 142 = 144 + 196 = 340 c2 = 182 = 324 340 < 34 → c2 < a2 + b2, and so the triangle is an acute triangle.
