Trigonometric function
Correlation between triangulation functions
![](image/eq11-02.gif)
Triangulation functions of 90 degrees interval
![](image/eq11-03.gif)
Addition theorem
![](image/eq11-04.gif)
Double angle
![](image/eq11-05.gif)
Half angle
![](image/eq11-06.gif)
Composition of sine function
![](image/eq11-07.gif)
alpha satisfies the following
![](image/eq11-08.gif)
Product --> Sum
![](image/eq11-09.gif)
Sum --> Product
![](image/eq11-10.gif)
Area of triangle
![](image/fig11-01.gif)
![](image/eq11-11.gif)
or,
![](image/eq11-12.gif)
where, ![](image/eq11-13.gif)
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