[calculus problem] given the function derivative and function value, find this function Find the function y = f (x). In the domain of definition (- π / 2, π / 2), the derivative is dy / DX = TaNx and satisfies the condition that f (3) = 5 The answer is: F (x) = ∫ (upper x, lower 3) tank DT + 5 My question: how is the upper and lower of ∫ determined? Why is the lower of ∫ 3? I thought the upper and lower of ∫ should be interval (here I think the upper and lower should be π / 2 and - π / 2) Great Xia, help to talk and guide maze! Thank you!

[calculus problem] given the function derivative and function value, find this function Find the function y = f (x). In the domain of definition (- π / 2, π / 2), the derivative is dy / DX = TaNx and satisfies the condition that f (3) = 5 The answer is: F (x) = ∫ (upper x, lower 3) tank DT + 5 My question: how is the upper and lower of ∫ determined? Why is the lower of ∫ 3? I thought the upper and lower of ∫ should be interval (here I think the upper and lower should be π / 2 and - π / 2) Great Xia, help to talk and guide maze! Thank you!

I have a way
If we know the derivative of a function, we can find a group of primitive functions, which are only one constant different from each other, as long as we make the integral constant pair to the upper sign
Then a set of primitive functions is x ^ 2 + C
As long as you construct a function such that C satisfies the condition