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In `Delta ABC`, right angled at A, `cos^(-1)((R )/(r_(2)+r_(3)))` isA. `30^(@)`B. `60^(@)`C. `90^(@)`D. `45^(@)` |
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Answer» Correct Answer - B `r_(2)+r_(3)=4R"cos"^(2)(A)/(2)` `angle A=90^(@)` `therefore cos^(-1)((R )/(r_(2)+r_(3)))` `=cos^(-1)((R )/(4"R cos"^(2)(A)/(2)))` `="cos"^(-1)(1)/(2)` `=60^(@)` |
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