What type of triangle is formed by joining the points d(7, 3), e(8, 1), and f(4, -1)?

Calculate the lengths of the sides of the triangle:

The triangle has three different sides, so it's a scalene triangle.

Now if c is the longest side of the triangle, and a and b are the shorter sides, then:
- if , the triangle is right
- if , the triangle is acute
- if , the triangle is obtuse

The longest side is 5.

The square of the longest side is equal to the sum of the squares of the shorter sides, so it's a right triangle.

The triangle is a right scalene triangle.