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Application Of Derivatives

Question
CBSEENMA12035584

Use differentials to approximate:
square root of 0.6 end root



Solution

Take straight y space equals square root of straight x comma space space space space straight x space space equals 0.64 comma space space space dx space equals space δx space equals space minus 0.04 space so space that space straight x space plus space straight delta space straight x space equals space 0.6
Now,        straight y plus δy space equals space square root of straight x plus δx end root space space space space space rightwards double arrow space space space δy space equals space square root of straight x plus δx end root space minus space straight y space equals space square root of 0.6 end root space space minus space 0.8
rightwards double arrow space space space space space space space space space space space space space square root of 0.6 end root space equals space δy space plus space 0.8                                       ...(1)
Now,    δy is approximately equal to dy
and            dy space equals space dy over dx dx space equals space fraction numerator 1 over denominator 2 square root of straight x end fraction dx space equals space fraction numerator 1 over denominator 2 square root of 0.64 end root end fraction left parenthesis negative 0.04 right parenthesis
                       equals negative fraction numerator 0.04 over denominator 2 space cross times space 0.8 end fraction space equals space minus fraction numerator 0.04 over denominator 1.6 end fraction space equals space minus 0.025
therefore space space space space space from space left parenthesis 1 right parenthesis comma space space space square root of 0.6 end root space equals space minus 0.025 plus 0.8 space equals space 0.775