Question

Dear ma'am/sir,
please help me to solve this question
please find attached​

Answer 1

90°

Step-by-step explanation:

AB=AC(given)

angleABC=angleACB( opposite angles of equal sides AB and AC)

angleBAC+angleABC+angleACB=180°(angle sum property of a triangle)

40°+angleABC+angleABC=180°(angleABC is on the place of angleACB because angleACB=angleABC)

40°+2angleABC=180°

2angleABC=180°-40°

2angleABC=140°

anlgeABC=140°/2

anlgeABC=70°

angleABC=angleACB=70°

angleABI=angleIBC= 1/2×angleABC=1/2×70°=35°(BI bisects angleABC)

angleACI=angleICB=1/2×angleACB=1/2×70°=45°

(IC bisects angleACB)

angleICB+angleIBC+angleBIC=180°(angle sum property of a triangle)

45°+45°+angleBIC=180°

90°+angleBIC=180°

angleBIC=180°-90°

angleBIC=90°

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