Question

A b c are jnternal angle of a triangle prrove that cos(b+c )=-cos a​

Answer 1

Answer:   If A, B, and C are angles of a triangle, how do I show that cos(B+C)=-cosA? 7 Answers ... Let ABC be a triangle with angle A = 90 degrees and AB = AC. ... A square XZYA is drawn inside that triangle, Y is on AC, X is on AB and Z is on BC

Answer 2

Answer:

a n c hnternal angle prove by making triangle

Step-by-step explanation:

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