Question:medium

Find the order and degree of the differential equation \(\left(\dfrac{d^2y}{dx^2}\right)^3 + \left(\dfrac{dy}{dx}\right)^2 + \sin\left(\dfrac{dy}{dx}\right) + 1 = 0\).

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Order = highest derivative present. Degree needs the equation to be a polynomial in the derivatives; sin(dy/dx) breaks that.
Updated On: Sep 23, 2026
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Solution and Explanation

Step 1: Scan the equation term by term for the highest derivative:
The terms present are $(d^2y/dx^2)^3$, $(dy/dx)^2$, $\sin(dy/dx)$ and a constant. The largest derivative order appearing anywhere is 2 (from $d^2y/dx^2$), so order $=2$.

Step 2: Try to write the equation as a pure polynomial:
A polynomial in $y', y''$ would only allow whole-number powers of these derivatives added together, never a derivative passed through a transcendental function like $\sin(\cdot)$. Expanding $\sin(dy/dx)$ as a Taylor series gives infinitely many powers of $dy/dx$, not a finite polynomial.

Step 3: Conclude:
Since the equation cannot be forced into polynomial form in the derivatives, the standard convention says the degree does not exist for this equation.

Final Answer:
Order is 2; degree is not defined. \[ \boxed{\text{Order} = 2,\ \text{Degree not defined}} \]
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