Question

5. Given the following triangle side lengths, identify the triangle as acute, right or obtuse. Show your work. a. 5 in, 6 in, 7 in b. 18 in 9 in, 12 in

Answer 1

When given 3 triangle sides:

1) Square all 3 sides.

2) Sum the squares of the 2 shortest sides.

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

if sum > 3rd side²   Acute Triangle

if sum = 3rd side²   Right Triangle

if sum < 3rd side²   Obtuse Triangle

a) 25, 36, 49
25 + 36 = 61
61 > 49
Acute Triangle

b) 81, 144, 324
81 + 144 = 225
225 < 324
Obtuse Triangle

Source:
http://www.1728.org/triantest.htm
(My website)