how do we do it ?

electric flux i suppose //

tanθ = R/L

charge through one slice of disc = dq= 3Q/L³ x²dx

since it is an uniformly charged solid cone,
the field due to the charge will be symmetrical about the central line .

and, the horizontal feilds will cancel each other, leaving only the vertical
component.

so lets take a disk and find its flux.

dφ = q/ ε₀ = 3Q/L³Îµ₀ x²dx

=> φ = ∫ 3Q/L³Îµ₀ x²dx (from x=0 to L)

=> φ = Q/ε₀.

(this is the most weird result i had expected.)

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