How would you evaluate the circumferential strain, εθ, at r = 0? What is this strain in...

How would you evaluate the circumferential strain, ε_θ, at r = 0? What is this strain in terms of the a’s given in Eq. (9.1.15). Hint: Elasticity theory tells us that the radial strain must equal the circumferential strain at r = 0.

Eq. (9.1.15).