[Math] sketch the region enclosed by the given curves and find its area

calculusdefinite integralsintegration

sketch the region enclosed by the given curves and find its area:

$$y=\frac 1x,\; y=x,\; y=\frac x4,\; x>0.$$

I have no problem sketching the area between the curves but there are three, and only one constant value, so I don't know what to put as my second a/b value. I tried using 1/x as a b value but that just gave me an equation answer and the answer isn't an equation.

edit: i forgot about the intersections as constant values. but now I see how to split them up.

This is chapter 6.1 calculus James Stewart btw (area between curves)

Best Answer

From Wolfram Alpha, we can sketch the curves to find the area of interest:

enter link description here

Note that we need to find the points of intersection: at $x = 0$ the lines $y = x, \;y = \frac x{4}$ intersect. At $x= 1$, the lines $y = x$ and $y = \frac 1x$ intersect. At $x = 2,$ the lines $y = \frac 1x $ and $y = \frac x4$ intersect. You can solve this by integrating between the relevant curves from $x = 0$ to $x = 1$, and likewise integrating between the relevant curves between $x = 1$ and $x = 2$, then summing: $$\int_0^1 \left(x - \frac x4\right)\,dx \quad + \quad \int_1^2 \left(\frac 1x - \frac x4\right)\,dx $$