Trigonometry: Sum and Difference Formulas
This is a free lesson from our course in Trigonometry
This lesson content introduces and walks you through the important concepts of sum and difference formulas for sine and cosine functions. The purpose and use of the sum, difference formulas have been explained by the instructor using video and with the help of some examples, practice questions with solution.
Sine of the quantity (A + B): multiply sin A by cos B and then add the multiplication product of cos A by sin B i.e.
     sin (A + B) = sin A cos B + cos A sin B
The difference identity i.e. sine of the quantity (A - B) can be worked by multiplying sin A by cos B and then subtracting cos A times sin B:
     sin(A - B) = sin A cos B - cos A sin B. (More text below video...)
<h2>Trigonometry - Sum and Difference Formulas</h2> <p>sum and difference formulas , video, sum formula, angles, learn, difference formulas, example, solution, sine function, cosine function, sin, cos, trigonometric identities, use of sum and difference formulas, practice questions, quizzes.</p> <p>sin (A + B) = sin A cos B + cos A sin B sin(A - B) = sin A cos B - cos A sin B. cos (A + B) = cos A cos B - sin A sin B cos (A - B) = cos A cos B + sin A sin B</p>
Other useful lessons:
Using Sum and Difference Formulas
Double and Half Angle Formulas
Using Double and Half Angle Formulas
(Continued from above)Similarly, the sum and difference formulas for cosine functions are as below:
     cos (A + B) = cos A cos B - sin A sin B
     cos (A - B) = cos A cos B + sin A sin B
These formulas can be used to find exact values of trigonometric ratios for the angles. For example, to calculate the exact value of cos 75, first write it as cos (45 + 30), then plug in the values of A = 45 and B = 30 in the formula cos (A + B) = cos A cos B - sin A sin B. The resulting expression is:
cos 75 = cos 45 cos 30 - sin 45 sin 30,
Now plug in the corresponding values for each and you'll get the answer i.e. cos 75 = (6 - 2)/4.
Winpossible's online math courses and tutorials have gained rapidly popularity since their launch in 2008. Over 100,000 students have benefited from Winpossible's courses... these courses in conjunction with free unlimited homework help serve as a very effective math-tutor for our students.
- All of the Winpossible math tutorials have been designed by top-notch instructors and offer a comprehensive and rigorous math review of that topic.
- We guarantee that any student who studies with Winpossible, will get a firm grasp of the associated problem-solving techniques. Each course has our instructors providing step-by-step solutions to a wide variety of problems, completely demystifying the problem-solving process!
- Winpossible courses have been used by students for help with homework and by homeschoolers.
- Several teachers use Winpossible courses at schools as a supplement for in-class instruction. They also use our course structure to develop course worksheets.
 Copyright © Winpossible, 2010 - 2011
Best viewed in 1024x768 & IE 5.0 or later version