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Solve dy/dx = y/x + tan(y/x)

Short answer

Homogeneous. Put y=vx to get cot v dv = dx/x. Integrate: ln|sin v| = ln|x|+ln c, so sin v = cx. Solution: sin(y/x) = cx.

Solve the differential equation dy/dx = y/x + tan(y/x).

The right side is a function of y/x, so the equation is homogeneous.

Substitution

Put y = vx, so dy/dx = v + x dv/dx. The equation becomes

v + x dv/dx = v + tan v x dv/dx = tan v

Separate and integrate

cot v dv = dx/x

ln|sin v| = ln|x| + ln c

sin v = cx

sin(y/x) = cx, where c is an arbitrary constant.

(Check: y = x sin⁻¹(cx) gives dy/dx = y/x + cx/√(1 − c²x²) = y/x + tan(y/x) ✓.)

✓ Answer checked by Claude Opus 5.5 (high effort)

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