Question

A triangle has a side lengths of 4cm,3cm, and 4cm. Classify its as acute, obtuse, or right.

Answer 1

When given 3 triangle sides, to determine if the triangle is acute, right or obtuse:

1) Square all 3 sides.

4, 3, 4, 

16, 9, 16

2) Sum the squares of the 2 shortest sides.

16 + 9 = 25

3) Compare this sum to the square of the 3rd side.

25 > 16

if sum > 3rd side²   Acute Triangle

So, it is an acute triangle.

Source:
http://www.1728.org/triantest.htm