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Trig Equations

  1. Feb 23, 2009 #1
    So, I know how to solve them in general, but this one in particular, what do you do when the sin or cos etc is squared?

    6sin^2 a - 11sin a + 4 = 0 , domain is from -360 until 360 degrees

    we learned that, you need to isolate sin a, and then find the possible angles. I just need to know how to isolate sin a.

    so i thought maybe this....

    6 (sin a + sin a) - 11sin a = -4

    but i dont know from here on....
    please help!! exam is coming up!
  2. jcsd
  3. Feb 23, 2009 #2


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    Science Advisor

    What? sin^2 a is (sin a)(sin a) NOT "sin a+ sin a"?

    Perhaps it would be simpler to replace sin a by y:
    6y^2- 11y+ 4= 0. Can you solve that quadratic equation? After finding solutions, that is, specific values for y, you can solve sin a= y.
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