Question bank/JEE Main/Mathematics

JEE MainMathematicsEasyDifferentiation

Let f and g be function satisfying f(0)=1, g(0)=0 and
f′(x)=g(x),g′(x)=f(x)f^{'}(x) = g(x),g^{'}(x) = f(x) then f

Show answer and solution
f′′(x)=f(x)f^{''}(x) = f(x)
⇒f(x)=Aex+Be−x\Rightarrow f(x) = Ae^{x} + Be^{- x}
A+B=1A + B = 1
f′(x)=Aex−Be−xf^{'}(x) = Ae^{x} - Be^{- x}
f′(0)=g(0)=0⇒A=Bf^{'}(0) = g(0) = 0 \Rightarrow A = B
f(x)=12(ex+e−x)f(x) = \frac{1}{2}(e^{x} + e^{- x})

Source: Grass-G / M-12 Mathematics Paper 2 Nov.docx

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