show that triangle ABC is isosceles if angle B=30 degree and C=120 degree
Answers
Answer:
remaining angle is of30 degrees so both angle of 30 degrees and called isosceles
Given : ΔABC
∠A = 120°
∠B = 30°
To Find : Show that triangle ABC is isosceles
Solution:
Triangle Angle sum theorem:
Sum of all the angles of a triangle is 180°
Hence in ΔABC
∠A + ∠B + ∠C = 180°
∠A = 120°
∠B = 30°
Substitute the values
120° + 30° + ∠C = 180°
=> 150° + ∠C = 180°
=> ∠C = 180° - 150°
=> ∠C = 30°
∠B = ∠C = 30°
Sides opposite to Equal angles in a triangle are equal
Hence AC = AB
As two sides of triangle are equal hence triangle is Isosceles
QED
Hence Proved
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