The course descriptions is : A theoretical course in calculus; emphasizing proofs and techniques. Trigonometric identities. Limits and continuity; least upper bounds, intermediate and extreme value theorems. Derivatives, mean value and inverse function theorems. Integrals; fundamental theorem; elementary transcendental functions. Techniques of integration. Taylor's theorem; sequences and series; uniform convergence and power series.
This course is using Spivak's calculus, but I'm also looking for another proof based book accompany with Spivak, thx
The Theory of The Calculus is called Mathematical Analysis ...Elementary Analysis for the R to R functions....so any of the very many books on Analysis should serve your purpose.