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

### NY Lost Funds

 clarity_ i used them for diff eq though TRWBW clarity_: in a lot of ways it turns out easier to do calculus with complex numbers, fewer special cases gaten Question: "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 thermoplyae Stuck where clarity_ is it normal to go through 3 calc classes without being exposed to calc w/ complex numbers? whaleofconfusion yes gaten thermoplyae: 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 whaleofconfusion i mean normally you'd see a little but not very much gaten i tried solving for k by integrating that equation, but i don't think that's right whaleofconfusion it is rightwhat is the numeric value of the integral of dT/dt from 0 to 25 mins? gaten 25 whaleofconfusion no gaten whaleofconfusion: you mean solve for k? whaleofconfusion yesthe answer is 5not k, but for the integral of dT/dt from 0 to 25the temperature increased from 5 degrees to 10 degrees gaten right. i plugged in T and R with 10 and 20 whaleofconfusion T is a function of t gaten ok right. temp is dependant on time merus TRWBW: On your advice I tried xdvi, and you're right, it's 5 times faster than any pdf viewer I have. soars http://textpaste.net/mj8e16 whaleofconfusion you don't plug in a value for itwhen you integrate the left side from 0 to 25 you get 5when you integrate the right side you get something involving various constants, and kand you set taht equal to 5 gaten wait, the left side is dT/dt which the integral is T, isnt it? whaleofconfusion yesand evaluated from 0 to 25 gaten (25) - (0) = 25...? whaleofconfusion no is that how you evaluate a definite integral? soars This is How Real Men Code .. gaten int(dT/dt) = T(b-a) right? whaleofconfusion nowhat is the integral of f from a to b, given that the indefinite integral of f is F? gaten F(b)-F(a) whaleofconfusion now use thathint: f = dT/dt gaten oooh ic. T is a function of time, like you told me. so its T(25) - T(0) = 10 - 5