Wize University Calculus 1 Textbook > Integrals

Antiderivatives of Trig Functions

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Antiderivatives (Indefinite Integral) of Trig Functions

Let kk be a nonzero constant. Then we have the following indefinite integral rules:
sin(kx)dx=1kcos(kx)+Ccos(kx)dx=1ksin(kx)+Csec2(kx)dx=1ktan(kx)+Csec(kx)tan(kx)dx=1ksec(kx)+Ccsc2(kx)dx=1kcot(kx)+Ccsc(kx)cot(kx)dx=1kcsc(kx)+C\begin{array}{|l|l|} \hline\\ \displaystyle\int\sin{(kx)}dx=-\dfrac{1}{k}\cos{( kx)}+C & \displaystyle\int\cos{ (kx)}dx=\dfrac{1}{k}\sin{( kx)}+C \\ \\ \hline\\ \displaystyle\int\sec^2{(kx)}dx=\dfrac{1}{k}\tan (kx)+C &\displaystyle\int\sec (kx)\tan (kx)dx=\dfrac{1}{k}\sec (kx)+C \\ \\ \hline\\ \displaystyle\int\csc^2(kx)dx=-\dfrac{1}{k}\cot (kx)+C & \displaystyle\int\csc (kx)\cot (kx)dx=-\dfrac{1}{k}\csc( kx)+C \\ \\ \hline \end{array}
Additionally
tanxdx=lncosx+Ccotxdx=lnsinxsecxdx=lnsecx+tanx+Ccscxdx=lncscx+cotx+C\begin{array}{|l|l|} \hline\\ \displaystyle \int\tan xdx=-\ln|\cos x|+C & \displaystyle \int \cot xdx=\ln|\sin x| \\ \\ \hline\\ \displaystyle\int \sec x dx=\ln|\sec x+\tan x| + C &\displaystyle \int \csc x dx=-\ln|\csc x+\cot x|+C \\ \\ \hline \end{array}

Wize Tip
These last four indefinite integrals can be found using future techniques of integration and are not always required to be memorized.

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Example: Trig Indefinite Integrals

Evaluate the following indefinite integral

1+tan2θ dθ\displaystyle \int\sqrt{1+\tan^2\theta} \ d\theta

1+tan2θ dθ\displaystyle \int\sqrt{1+\tan^2\theta} \ d\theta

=sec2θ dθ=\displaystyle \int\sqrt{\sec^2\theta} \ d\theta

=secθ dθ=\displaystyle \int\sec \theta \ d\theta

=lnsecθ+tanθ+C\displaystyle=\ln|\sec \theta+\tan \theta| + C
Evaluate the following indefinite integral

(x2+2sinx3cosx)dx\displaystyle \int( x^2+2\sin x-3\cos x )dx
Evaluate the following indefinite integral

(sec2x)(cos22x)dx\displaystyle \int (\sec 2x)( \cos^2 2x)dx

Extra Practice