1.

If y = sin(lnx),  then which one of the following is correct?a. d2y/dx2 + y = 0b. d2y/dx2 = 0c. x2(d2y/dx2) + x(dy/dx) + y = 0d. x2(d2y/dx2) - x(dy/dx) + y = 0

Answer»

Correct option c. x2(d2y/dx2) + x(dy/dx) + y = 0  

Explanation:

y = sin(logx) ⇒ dy/dx = (cos(logx))/x

⇒ x(dy/dx) = cos(logx)

Again, Differentiating,

x(d2y/dx2) + dy/dx = (sinlogx/x) = -y/x

⇒ x2(d2y/dx2) + x(dy/dx) + y = 0



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