## swin2013 3 years ago Related Rates question?

1. swin2013

At what rate is the area of the triangle formed by the ladder wall and the ground changing at that moment? i already know that dy/dt is -12 cm/sec

2. baldymcgee6

3. swin2013

A 13 ft ladder is leaning against a house when its base starts to slide away. By the time the base is 12 ft from the house, the base is moving at the rate 5 ft/sec

4. baldymcgee6

|dw:1352178476520:dw|

5. swin2013

yep, well i already found dy/dt and i was deriving dA/dt but it seemed wrong

6. swin2013

i got 1/2 db/dt * h + dh/dt *b

7. baldymcgee6

|dw:1352178791974:dw|

8. baldymcgee6

|dw:1352179052193:dw|

9. swin2013

10. swin2013

how did you do that? did you just took the derivative inside and distribute the half sign?

11. baldymcgee6

oops o missed something while differentiating the area formula

12. swin2013

ok but did you do product rule?

13. baldymcgee6

yes

14. baldymcgee6

but wrong.. lol

15. baldymcgee6

|dw:1352179446697:dw|

16. swin2013

do you have to distribute?

17. baldymcgee6

no theres nothing to distribute

18. swin2013

then why do you have 0.5 multiplied on each portion? isn't 1/2 a constant?

19. baldymcgee6

just type that into your calc... and you should get it.

20. baldymcgee6

0.5 is a constant that could be factored out.. but there is no point

21. swin2013

i did. but if i didn't distribute, i would get the wrong answer

22. swin2013

oh no i got it/ lol nvm thanks!

23. baldymcgee6

:)