A student approximates the integral ${\int }_a^b{\sin }^{2}x\text{d}x$ using the trapezium rule with $4$ strips. The resulting approximation is an overestimate.

Which of the following is/are necessarily true?

I If the student approximates ${\int }_{-b}^{-a}{\sin }^{2}x\text{d}x$ in the same way, the result will be an overestimate.

II If the student approximates ${\int }_a^b{\cos }^{2}x\text{d}x$ in the same way, the result will be an underestimate.