Compute using Trig Identities 4

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Taught by YourMathGal
  • Currently 4.0/5 Stars.
1399 views | 1 rating
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Lesson Summary:

In this lesson, Julie Harland demonstrates how to use trig identities to make computations. Using the formula for cosine of 2A and substituting the value of sine of A over 2, she shows how to find the value of cosine of A. She also emphasizes that every problem is different and requires a unique approach. To find the value of sine or tangent of A, she suggests using the Tha-Green theorem and understanding the quadrant in which A falls.

Lesson Description:

Using Trig Identities to make computations.

More free YouTube videos by Julie Harland are organized at

Questions answered by this video:
  • How do you make computations using trig identities?
  • If sin(A/2) = 1/5, what does cosA equal?
  • How do you find cosA if you know sin(A/2)?
  • Staff Review

    • Currently 4.0/5 Stars.
    This lesson shows how to compute cos of an angle if you know the value of sin of half the angle. The double angle identity is used to find the angle. All steps involved in making the computations are shown and explained very clearly in this lesson. Check out the next lessons in this series for more example problems.