#math - Mon 2 Apr 2007 between 04:25 and 04:59

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clarity_i used them for diff eq though
TRWBWclarity_: in a lot of ways it turns out easier to do calculus with complex numbers, fewer special cases
gatenQuestion: "when a cold drink is taken from a fridge, its temperature is 5 deg C. After 25 mins in a 20 deg C room its temperature has increased to 10 deg C. What is the temp of the drink after 50 mins, and when will the temp reach 15 deg C." I know i have to use newtons' cooling equation, but im stuck
thermoplyaeStuck where
clarity_is it normal to go through 3 calc classes without being exposed to calc w/ complex numbers?
whaleofconfusionyes
gatenthermoplyae: the whole thing really. so far ive only got that dT/dt = k(T - R), T being the temp of the drink, and R being the temp of the room
whaleofconfusioni mean normally you'd see a little but not very much
gateni tried solving for k by integrating that equation, but i don't think that's right
whaleofconfusionit is right
what is the numeric value of the integral of dT/dt from 0 to 25 mins?
gaten25
whaleofconfusionno
gatenwhaleofconfusion: you mean solve for k?
whaleofconfusionyes
the answer is 5
not k, but for the integral of dT/dt from 0 to 25
the temperature increased from 5 degrees to 10 degrees
gatenright. i plugged in T and R with 10 and 20
whaleofconfusionT is a function of t
gatenok right. temp is dependant on time
merusTRWBW: On your advice I tried xdvi, and you're right, it's 5 times faster than any pdf viewer I have.
soarshttp://textpaste.net/mj8e16
whaleofconfusionyou don't plug in a value for it
when you integrate the left side from 0 to 25 you get 5
when you integrate the right side you get something involving various constants, and k
and you set taht equal to 5
gatenwait, the left side is dT/dt which the integral is T, isnt it?
whaleofconfusionyes
and evaluated from 0 to 25
gaten(25) - (0) = 25...?
whaleofconfusionno is that how you evaluate a definite integral?
soarsThis is How Real Men Code ..
gatenint(dT/dt) = T(b-a) right?
whaleofconfusionno
what is the integral of f from a to b, given that the indefinite integral of f is F?
gatenF(b)-F(a)
whaleofconfusionnow use that
hint: f = dT/dt
gatenoooh ic. T is a function of time, like you told me. so its T(25) - T(0) = 10 - 5

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