Question

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

Answer 1

anybody ??? :(

Answer 2

you know agent00smith ?

Answer 3

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

Answer 4

chain rule ?

Answer 5

but we have t differentiate A with respect to ??

Answer 6

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

Answer 7

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

Answer 8

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

Answer 9

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

Answer 10

Differentiate with respect to time*

Answer 11

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

Answer 12

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

Answer 13

im not clear with that

Answer 14

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

Answer 15

Woops, product rule! :O

Answer 16

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

Answer 17

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

Answer 18

urmmm let me try that

Answer 19

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

Answer 20

yay team \:D/

Answer 21

my mentors :)

Answer 22

ah yes, my bad