Question

Study the given figure and identify the following triangles.

(a) equilateral triangle
(b) isosceles triangles
(c) scalene triangles
(d) acute triangles
(e) obtuse triangles
(f) right triangles

Answer 1

(a) BC = 1 + 1 + 1 + 1 = 4 cm

AB = AC = 4 cm

∆ABC is an equilateral triangle.

(b) ∆ABC and ∆AEF are isosceles triangles.

Since AB = AC = 4 cm

Also AE = AF.

(c) In a scalene triangle, no two sides are equal.

∆AEB, ∆AED, ∆ADF, ∆AFC, ∆ABD, ∆ADC, ∆ABF and ∆AEC are scalene triangles.

(d) In an acute-angled triangle all the three angles are less than 90°

∆ABC, ∆AEF, ∆ABF and ∆AEC are acute-angled triangles.

(e) In an obtuse-angled triangle any one of the angles is greater than 90°

∆AEB and ∆AFC are obtuse angled triangles.

(f) In a right triangle, one of the angles is 90°

∆ADB, ∆ADC, ∆ADE and ∆ADF are right-angled triangles.