MAT244--2018F > MAT244--Lectures & Home Assignments

integral problems

(1/1)

chloe:
\begin{equation}

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

\end{equation}

Chuanxin Zhang:
\begin{equation}

\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})\\



\end{equation}



let  m=cos3t

\begin{equation}
\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}\\


\end{equation}

Victor Ivrii:
$*$ IS N OT A SIGN OF MULTIPLICATION

Chuanxin Zhang:
Fixed! I thought * was the multiplication sign by default:(

Navigation

[0] Message Index