Shortcut Trick
Calculate the squared lengths of the sides to identify the triangle type quickly.
Side 12 = (4−1)2 + (1−1)2 = 32 + 02 = 9
Side 22 = (3−1)2 + (5−1)2 = 22 + 42 = 20
Side 32 = (3−4)2 + (5−1)2 = (−1)2 + 42 = 17
Since all squared lengths are different (9 ≠ 20 ≠ 17), all sides are unequal.
Also, no two squared lengths sum to the third (9 + 17 ≠ 20), so it is not right-angled.
∴ The correct answer is Scalene triangle.
Alternate Method
Given: Vertices of the triangle are A(4, 1), B(1, 1), and C(3, 5).
Formula Used: Distance between two points (x1, y1) and (x2, y2) = √((x2−x1)2 + (y2−y1)2)
⇒ Length of side AB = √((4−1)2 + (1−1)2) = √(32 + 02) = 3 units
⇒ Length of side BC = √((3−1)2 + (5−1)2) = √(22 + 42) = √20 units
⇒ Length of side AC = √((3−4)2 + (5−1)2) = √((−1)2 + 42) = √17 units
⇒ Comparing the sides: 3 ≠ √20 ≠ √17. Since all sides are unequal, it is a Scalene triangle.
⇒ Checking Pythagoras Theorem: 32 + (√17)2 = 9 + 17 = 26. Since 26 ≠ (√20)2, it is not a right-angled triangle.
∴ The correct answer is Scalene triangle.
Additional Information
Scalene Triangle
A triangle in which all three sides have different lengths and all three angles have different measures.
Isosceles Triangle
A triangle that has two sides of equal length and two equal angles opposite those sides.
Right-Angled Triangle
A triangle with one angle exactly 90°. It must satisfy the condition a2 + b2 = c2, where c is the longest side.
Distance Formula
The distance between two points in a 2D plane is given by d = √((x2−x1)2 + (y2−y1)2).