# AP Calculus BC : Riemann Sum: Left Evaluation

## Example Questions

### Example Question #50 : Integrals

Find the Left Riemann sum of the function

on the interval  divided into four sub-intervals.

Explanation:

The interval  divided into four sub-intervals gives rectangles with vertices of the bases at

For the Left Riemann sum, we need to find the rectangle heights which values come from the left-most function value of each sub-interval, or f(0), f(2), f(4), and f(6).

Because each sub-interval has a width of 2, the Left Riemann sum is

### Example Question #51 : Integrals

Given a function , find the Left Riemann Sum of the function on the interval  divided into three sub-intervals.

Explanation:

In order to find the Riemann Sum of a given function, we need to approximate the area under the line or curve resulting from the function using rectangles spaced along equal sub-intervals of a given interval. Since we have an interval  divided into  sub-intervals, we'll be using rectangles with vertices at

To approximate the area under the curve, we need to find the areas of each rectangle in the sub-intervals. We already know the width or base of each rectangle is  because the rectangles are spaced  units apart. Since we're looking for the Left Riemann Sum, we want to find the heights  of each rectangle by taking the values of each leftmost function value on each sub-interval, as follows:

Putting it all together, the Left Riemann Sum is

.

### Example Question #52 : Integrals

Given a function , find the Left Riemann Sum of the function on the interval  divided into four sub-intervals.

Explanation:

In order to find the Riemann Sum of a given function, we need to approximate the area under the line or curve resulting from the function using rectangles spaced along equal sub-intervals of a given interval. Since we have an interval  divided into  sub-intervals, we'll be using rectangles with vertices at

To approximate the area under the curve, we need to find the areas of each rectangle in the sub-intervals. We already know the width or base of each rectangle is  because the rectangles are spaced  unit apart. Since we're looking for the Left Riemann Sum, we want to find the heights  of each rectangle by taking the values of each leftmost function value on each sub-interval, as follows:

Putting it all together, the Left Riemann Sum is

Explanation:

Explanation:

Explanation:

Explanation:

Explanation: