## byerskm2 3 years ago Sketch the points given. Use rectangles to estimate the distance traveled by the rocket over the first 120 seconds as directed. (a) ... using 3 subintervals of equal width and the midpoint for sample points. http://i48.tinypic.com/65ac1e.jpg

1. byerskm2

I tried using the rieman sum midpoint but I keep getting it wrong!!!!

2. satellite73

how are you supposed to divide 140 in to three sub intervals? got me.

3. byerskm2

It changed it to 120

4. satellite73

i guess each has length of \(46\tfrac{2}{3}\) and you take the midpoint so first sample point would be at \(23\tfrac{1}{3}\)

5. byerskm2

you just ignore the 140 I guess

6. satellite73

well that makes it easier

7. byerskm2

so it would be 30

8. satellite73

no one third of 120 is 40

9. byerskm2

oh crap I thought it was four intervals

10. satellite73

one interval would be \([0,40]\) next would be \([40,80]\) and last would be \([80,120]\) you would sample as \(20,60,100\)

11. satellite73

*sample AT

12. byerskm2

so it would be 40[ f(20)+f(60)+f(100)] ?

13. satellite73

yes that should do it

14. byerskm2

@satellite73 but it talks about rectangles so for each interval do I just do the X*y?

15. byerskm2

It's still wrong. :(

16. satellite73

yes it is just rectangles, base times height

17. satellite73

is the last 140,8 gone or something?

18. byerskm2

40[(2*20)+(4*20)+(8*20)]

19. byerskm2

I don't know, but this is what I did using base times height

20. byerskm2

and it's still wrong

21. satellite73

oh i see what you did wrong

22. satellite73

the base if 40, the height is 2, 4 and 8 respectively

23. satellite73

you wrote \(40[ f(20)+f(60)+f(100)]\)

24. satellite73

that is correct, and \(f(20)=2,f(60)=4, f(100)=8\) so it should be \[40(2+4+8)\]

25. byerskm2

OH -_- wow. thanks :P I knew I was doing something too much

26. byerskm2

:)