1.

किसी `triangleABC` में यदि `A + C = 2B` तो सिद्ध करे कि `2 cos""(A-C)/(2) = (a+c)/(sqrt(a^(2) -ac + c^(2)))`

Answer» `because A + B +C = 180^(@) therefore 2B + B = 180^(@)` या, `B = 60^(@)`
अब, `cosB = (c^(2) + a^(2))/(2ca)` या, `cos 60^(@) = (c^(2) + a^(2) -b^(2))/(2ca)`
या, `(1)/(2) = (c^(2) + a^(2) - b^(2))/(2ca)` या, `a^(2) - ac + c^(2) = b^(2)" "...(1)`
अब दायाँ पक्ष ` = (a+b)/(sqrt(a^(2) -ac +c^(2)) ) = (a+c)/(b)` [(1) से]
अब `a = ksinA, b = ksinB, c = ksinC` रखकर आगे बढ़े |


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