Question

in given figure if angle A = 40° and angle B= 70° then find angle BCE

Answer 1

In ΔABC, ∠A + ∠B + ∠C = 180°

implies ∠C = 180° - 70° - 40° = 70°

According to figure, ACE is a straight line so ∠ACE = 180°

implies ∠ACB + ∠BCE = 180°

∠BCE = 180° - 70° = 110°

Answer 2

In ∆ABC
<BAC + <ABC+ <BCA = 180° (Sum of a triangle)
40°+70°+<BCA = 180°
110°+ <BCA = 180°
<BCA = 180°-110°
<BCA = 70°.
<BCA = <DCE = 70°. (Vertical opposite angle)

<DCE + <BCE = 180° (Linear pair)
70°+ <BCE = 180°
<BCE = 180°-70°
<BCE = 110°



< = angle sign




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