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In a triangle ABC , the line joining the circumcentre and incentre is parallel to BC, then Cos B + Cos C is equal to: |
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Answer» Let `r` is the radius of the incircle and `R` is the radius of circumcentre. As we are given line joining the circumcentre and incentre is parallel to BC in `Delta ABC`. `:. r = RcosA=> r/R = cosA->(1)` Also, we know the property, `cosA+cosB+cosC = 1+r/R` From (1), `cosA+cosB+cosC = 1+ cosA` `:. cosB+cosC = 1` |
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