Question

What is the area of an elementary horizontal strip of length \[x\] and infinitesimally small width \[dy\]?

Options

• \[dA=\int_c^d x\,dy\]

• \[dA=\left|\int_a^b f(x)\,dx\right|\]

• \[dA=y\cdot dx\]

• \[dA=x\cdot dy\]

Answer 1

A horizontal elementary strip has length \[x\] and width \[dy\]. Hence its area is \[dA=x\cdot dy\].