4. Integration: Basic Trigonometric Forms

by M. Bourne

In this section, we obtain the following integral formulas by reversing the formulas for differentiation of trigonometric functions that we met earlier:

math expression

We now apply the power formula to integrate some examples.

.

Example 1: Integrate: math expression


Answer


Example 2: Integrate: math expression


Answer


Integral formulas for some other trigonometric functions: (These are obtained by just reversing the differentiation process).

math expression


Example 3: Integrate: math expression


Answer


NOTE: The above formulas were obtained by reversing the differentiation process.

 

Further Integrals

Now, if we want to find math expression, we note that

math expression

math expression


Similarly, it can be shown that

math expression

Hence, we can summarise that :

math expression


Example 4: Integrate: math expression


Answer


Example 5: Integrate: math expression


Answer


Example 6: Find the area under the curve of y = sin x from x = 0 to math expression.


Answer

 

Exercises

Integrate each of the given functions:

1. math expression


Answer


2. math expression


Answer


3. If the current in a certain electric circuit is math expression, find the expression for the voltage across a 500-mF capacitor as a function of time. The initial voltage is zero. Show that the voltage across the capacitor is 90°out of phase with the current.


Here is the LiveMath solution to this problem.

LIVEMath


Answer


4. A force is given as a function of the distance from the origin as

math expression

Express the work done by this force as a function of x if W = 0 for x = 0.


Answer



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