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# Differentiating C3 watch

1. how to differentiate this 20(1-e^-0.2t) when t=2 to get the answer 4e^-0.2t ?!!
I really tried many times but could not this answer >_<
Any help? Thank you
2. (Original post by yoomi)
how to differentiate this 20(1-e^-0.2t) when t=2 to get the answer 4e^-0.2t ?!!
I really tried many times but could not this answer >_<
Any help? Thank you
Expand the brackets and differentiate each term individually (hint: 20 differentiated disappears so all you're actually differentiating is -20e^-0.2t)
3. (Original post by smartalan73)
Expand the brackets and differentiate each term individually (hint: 20 differentiated disappears so all you're actually differentiating is -20e^-0.2t)
I just did it again and figured it out lol I dunno what I have done wrong before
Thank you anyway
4. (Original post by yoomi)
how to differentiate this 20(1-e^-0.2t) when t=2 to get the answer 4e^-0.2t ?!!
I really tried many times but could not this answer >_<
Any help? Thank you
20(1-e^-0.2t) = 20-20e^-0.2t. differentiating with respect to t. use the chain rule. differential of e^t = e^t. so differential of e^-0.2t = e^-0.2t x -0.2 (differential of -0.2t). therefore differential of 20-20e^-0.2t = -20e^-0.2t x -0.2 = 4e^-0.2t. Then sub t=2 into the result.
5. y= ke^nx

dx/dy kn e^nx

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