Name the types of following triangles:
(a) Triangle with lengths of sides 7 cm, 8 cm and 9 cm.
(b) Δ ABC with AB = 8.7 cm, AC = 7 cm and BC = 6 cm.
(c) Δ PQR such that PQ = QR = PR = 5 cm.
(d) Δ DEF with m ∠D = 90°.
(e) Δ XYZ with m∠Y = 90° and XY = YZ.
(f) Δ LMN with m∠L = 30°, m∠M = 70° and m∠N = 80°.
(a) It is a scalene triangle as it has all unequal sides.
A scalene triangle is triangle with all three unequal sides.
(b) ∆ABC is a scalene triangle as it has three unequal sides and according to the property of triangle only scalene triangle has all unequal sides.
(c) ∆PQR is an equilateral triangle as all sides of the triangle is equal and according to the property of equilateral triangle has all equal sides.
(d) ∆DEF Right-angle triangle as it has ∠D = 90° and according to the property of right angle triangle it has one right angle that is 90°.
(e) ∆XYZ Right-angled isosceles angle as it has one right angle of 90° and two equal sides and according to the property of right-angled isosceles triangle is has one right angle with two equal sides.
(f) ∆LMN is an acute angle as it has all the angles less than 90° and according to the property of acute angle it is a triangle with all three angles acute (less than 90°).