Developing the sine and cosine of the sum of two angles
- Author:
- Alfonso Garcia, Lee Robinson
This is one of the compound angle formulae in the course.
You can use paper and pencil to follow.
Click on the green arrow to explore the development of the sine of the sum of two angles.
The initial screen is step 0, with each subsequent step being 1, 2, etc.
Follow each step in detail so you can answer the questions that follow.
1. About the inscribed right angle triangle. Refer to step 3.
Explain why the adjacent and opposite sides of this triangle are and ?
2. About the right angle triangle below the initial triangle. Refer to step 4.
Explain why the adjacent and opposite sides of the triangle at the bottom (the one with angle ) are and Hint: Use the definition of the cosine and sine ratios of angle in this triangle and keep in mind that you are finding sides.
3. The sides shown on step 5
Explain why these sides are labeled and ?
4. The sides shown on step 6
Explain the labels on the last two sides, meaning and
5. Making sense of the formulae. Refer to the steps 7 and onward
Explain how the compound angle formulae for the sine and cosine of the sum of two angles are finally determined based on the diagram and on previous steps.