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Wednesday, December 06, 2006

Wednesday, December 6, 2006
In today's lesson, we learned how to use the Law of Cosines to solve SSS and SAS (angle sandwich) problems!

If you have any question regarding a problem in this lesson, please post a comment and I will discuss your question in class tomorrow.
Mrs. S

posted by Mrs. S. at 1:38 PM

1 Comments:

  • In Today's Lesson, 3.2, we learned about SSS(Side side side) and SAS (Side Angle Side).
    The Law of Cosines formula that we use is: C^2=a^2+b^2-2ab Cos C (this is used for SAS), and Cos C= a^2+b^2-c^2/2ab (Uses for SSS).
    The three tips for solving for SAS triangles is: 1)Find the missing side first by using Law of Cosines. 2)Find the smaller of the two missing angles using the Law of Sines. 3)Find the third angle using geometry.
    For SSS triangles 1) Find the largest angle first using the Law of Cosines. 2)Find either the remaining angles using the Law of Sines.3) Find the third angle using geometry.
    EX.1 from the PowerPoint:
    Find the three angles of the triangle whose sides have lengths a=8,b=19,c=14.
    Step 1: Determine the case and then draw your triangle (it is SSS).
    Step 2: Label the given parts and find the largest angle first (Angle B is the largest because side b is the largest).
    Step 3: Use Law of Cosines to find angle B (Cos B= 8^2+14^2- 19^2/2*8*14 which equals -.4508), then used the reciprocal of Cosine to find the angle (116.8 degrees)
    Step 4:Find angle A
    Now u can use the Law of Sines to find angle A because now you have angle B to set it equal to.
    (Sin A/8=Sin116.8/19...which is 22.1).
    Step 5: Use Geometry to find the last angle (41.1)
    HOMEWORK: page 287 1-16,31-34

    By Anonymous Anonymous, at 8:58 PM  

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