## Ika_Kim Group Title somebody please help me..got test tonight but still dunn how to solve this... The base of a triangle increases at the rate 2cm per second, and height decreases at the rate of 1/2cm per second.Find the rate of change f its area when the base and height are of length 5cm... ? T.T helpp one year ago one year ago

1. Ika_Kim Group Title

anybody ??? :(

2. Ika_Kim Group Title

you know agent00smith ?

3. agent0smith Group Title

hmm.... we know $A = 0.5 b h$ $\frac{ db }{ dt } = 2 (cm/s)$ $\frac{ dh }{ dt }= -0.5 (cm/s)$ We need $\frac{ dA }{ dt } = ?$

4. Ika_Kim Group Title

chain rule ?

5. Ika_Kim Group Title

but we have t differentiate A with respect to ??

6. agent0smith Group Title

Yeah that's what i'm trying to think of...

7. Ika_Kim Group Title

o.O ok ... i really dunno how to relate that

8. zepdrix Group Title

Hmm are we assuming this is a right triangle? :o

9. zepdrix Group Title

I guess it would have to be, otherwise we need more information. :) Looks like agent was on the right track. Both $$\large b$$ and $$\large h$$ are variables. Just apply the product rule! :D

10. zepdrix Group Title

Differentiate with respect to time*

11. agent0smith Group Title

Yeah that's what I was thinking... differentiate A wrt t

12. Ika_Kim Group Title

huh ??? yeahh differentiate wrt time . that is wwhat we want to find

13. Ika_Kim Group Title

im not clear with that

14. agent0smith Group Title

But then that seems to make the actual values of the base and height unnecessary, but maybe that's okay.... $\frac{ dA }{ dt} = 0.5 \frac{ db }{ dt}\frac{ dh }{ dt}$

15. zepdrix Group Title

Woops, product rule! :O

16. zepdrix Group Title

$\large A=\frac{1}{2}bh$$\large A'=\frac{1}{2}b'h+\frac{1}{2}bh'$Something like that, yes? :D

17. Ika_Kim Group Title

huhh ????? how can...i dont undrstand...

18. Ika_Kim Group Title

urmmm let me try that

19. Ika_Kim Group Title

wow.....yeahh!!! correct answer !!! greatt !! thank you so much guys ! love uollsz!! :D

20. zepdrix Group Title

yay team \:D/

21. Ika_Kim Group Title

my mentors :)

22. agent0smith Group Title