Trigonometry: Using Double and Half Angle Formulas
 This is a free lesson from our course in Trigonometry

 This lesson walks you through how to use double and half angle formulas. It has been explained by the instructor using video and with the help of some examples, practice questions with solution. Double and Half-Angle formulas are very useful in trigonometric applications e.g. rational functions of sine and cosine will be very hard to integrate without these formulas. Similarly it would be useful to reduce the degree of difficulty, where functions involving powers of sine and cosine are hard to integrate. Also the Double-Angle formulas may be used to generate easily the Half-Angle formulas. (More text below video...)
Other useful lessons:
 Sum and Difference Formulas Using Sum and Difference Formulas Double and Half Angle Formulas
(Continued from above)  You'll learn the steps now; how to find out the value of sin 2 and sin 2, if the value of cos  is known and similarly to find the value of sin /2 and cos /2, if the value of cos is known. For example, cos 15 can be evaluated using the formula
cos (A/2) = (1 + cos A)/2.
cos (30/2) = (1 + cos 30)/2,
Substituting cos 30 = 3/2, you'll get the answer {(2 + 3)}/2.
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