Let f(x,y)=tan(6r-4), where r²=x²+y². Evaluate ∂f/∂x at (x,y) = (1,2)

Mistake: you may either type f(x,y)=tan[6sqrt(x^2+y^2)-4] or f(r)=tan(6r-4).

F(x,y)=tan[6sqrt(x^2+y^2)-4]=>
Fx={cos^2[6sqrt(x^2+y^2)-4][
6x/sqrt(x^2+y^2)]+sin^2[6sqrt(x^2+y^2)
-4][6x/sqrt(x^2+y^2)]}/
cos^2[6sqrt(x^2+y^2)-4]=>
Fx=[6x/sqrt(x^2+y^2)][1/cos^2[
6sqrt(x^2+y^2)-4]=>
Fx=(6x)sec^2[6sqrt(x^2+y^2)-4]/
sqrt(x^2+y^2)=>

Fx[(1,2)]=6sec^2[6sqrt(5)-4]/sqrt(5)=
Fx[(1,2)]=(6/5)sqrt(5)sec^2[6sqrt(5)-4…
Fx[(1,2)]=2.68347 approximately.

Where Fx=the partial derivative of F with respect to x.