In calculus, the indefinite integral of function f, or the original function or the inverse derivative, is a function f whose derivative is equal to f, that is, the relationship between indefinite integral and definite integral of F'= F is determined by the basic theorem of calculus. Where f is the indefinite integral of f, according to Newton-Leibniz formula, the calculation of definite integral of many functions can be simply carried out by finding indefinite integral. 1, the indefinite integral of the sum of functions is equal to the sum of indefinite integrals of each function; That is, if the original functions of functions f(x) and g(x) exist, then 2. When solving indefinite integral, the constant factor in the integrand function can be mentioned outside the integral symbol. That is, if the original function of function f(x) exists and k is a non-zero constant, then