Question
Function
Find the first partial derivative with respect to c
Find the first partial derivative with respect to r
∂c∂ϕ=r1
Simplify
ϕ=rc
Find the first partial derivative by treating the variable r as a constant and differentiating with respect to c
∂c∂ϕ=∂c∂(rc)
Use differentiation rule ∂x∂(g(x)f(x))=(g(x))2∂x∂(f(x))×g(x)−f(x)×∂x∂(g(x))
∂c∂ϕ=r2∂c∂(c)r−c×∂c∂(r)
Use ∂x∂xn=nxn−1 to find derivative
∂c∂ϕ=r21×r−c×∂c∂(r)
Use ∂x∂(c)=0 to find derivative
∂c∂ϕ=r21×r−c×0
Any expression multiplied by 1 remains the same
∂c∂ϕ=r2r−c×0
Any expression multiplied by 0 equals 0
∂c∂ϕ=r2r−0
Removing 0 doesn't change the value,so remove it from the expression
∂c∂ϕ=r2r
Solution
More Steps

Evaluate
r2r
Use the product rule aman=an−m to simplify the expression
r2−11
Reduce the fraction
r1
∂c∂ϕ=r1
Show Solution

Solve the equation
Solve for c
Solve for r
c=ϕr
Evaluate
ϕ=rc
Swap the sides of the equation
rc=ϕ
Cross multiply
c=rϕ
Solution
c=ϕr
Show Solution
