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### Messages - Chuanxin Zhang

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##### MAT244--Lectures & Home Assignments / Re: integral problems
« on: November 11, 2018, 01:43:07 PM »
Fixed! I thought * was the multiplication sign by default:(

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##### MAT244--Lectures & Home Assignments / Re: integral problems
« on: November 11, 2018, 12:56:16 AM »

\int \frac{-\sin{3t}\times9\sec^2{3t}}{3} \,dt\\

= \int \frac{-3sin{3t}}{cos^2{3t}} \,dt\\
=\int \frac{1}{cos^2{3t}} \,d(cos{3t})\\

let  m=cos3t

\int \frac{1}{cos^2{3t}} \,d(cos{3t})\\
=\int \frac{1}{cos^2{3t}} \,dm\\
=\int \frac{1}{m^2}\,dm\\
=\frac{-1}{m}\\
=\frac{-1}{cos3t}\\

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##### MAT244--Misc / Question about the lecture section
« on: September 25, 2018, 11:28:54 PM »
I'm just wondering that can you go to other lecture although you enrolled in other section, because some lecture pace is quite slow, requires more self-learning.

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