Given side lengths 5, 5, 6, classify the triangle.

Given side lengths 5, 5, 6, classify the triangle.

• A. Scalene
• B. Isosceles
• C. Equilateral
• D. Right-angled

Answer: (B)

Two sides have the same length, so this triangle is isosceles. Here the equal sides are 5 and 5, with the third side 6. The triangle is valid because 5 + 5 > 6, and the other sums also satisfy triangle inequality. It isn’t right-angled because a right triangle would satisfy 5^2 + 5^2 = 6^2, which is 50 ≠ 36. It isn’t equilateral since not all three sides are equal, and it isn’t scalene since two sides are equal. So the classification is an isosceles triangle.

Two sides have the same length, so this triangle is isosceles. Here the equal sides are 5 and 5, with the third side 6. The triangle is valid because 5 + 5 > 6, and the other sums also satisfy triangle inequality. It isn’t right-angled because a right triangle would satisfy 5^2 + 5^2 = 6^2, which is 50 ≠ 36. It isn’t equilateral since not all three sides are equal, and it isn’t scalene since two sides are equal. So the classification is an isosceles triangle.