Question

In a triangle angle A= angle C,B=120degree BC=4cm find angle A

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Answer 1

Answer:

according angle sum property of triangle ,

angle A + angle B + angle C = 180°

and angle A = angle B..let it be x .then

x + 120° +x = 180

120 + 2x = 180

2x = 180-120

2x = 40

x = 40/2

x = 20°

thus angle A and C will be 20°

Answer 2

Answer:

Given : AB = 6 cm, BC = 4 cm. and ∠B = 120°

To construct: Incircle of ΔABC Steps of construction :

(1) Draw a line segment BC = 4 cm

. (2) Construct a ray making an angle of 120° at B of BC. Cut AB = 7 cm.

(3) Join A to C, and obtain ΔABC.

(4) Now bisects ∠ABC and ∠BCA that to intersect at O.

(5) Draw OD ⊥ AC and with O as centre and OD as radius draw a circle which touches three sides of ΔABC. This is the in circle of ΔABC