Math hw... Please help!! (trig)

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Joined: 13 Dec 2008
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26 Apr 2009, 6:49 pm

I got this question on my homework, and I didnt know how to do it....

For angle θ find all values in degrees and radians over the interval (0, 2π) that satisfy the following trig equation: 8 sin²θ + 10sinθ =3

I tried google, but I couldnt find anything that helps....
Thank you very much!

MathGirl
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26 Apr 2009, 7:25 pm

this doesn't really belong in the autism discussion... why not try yahoo answers?

Kangoogle
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26 Apr 2009, 7:31 pm

Hint : Make the substitution sin (theta) = u, solve the quadratic then find the possible values of theta which are equal to the values of u that you found.

MathGirl
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26 Apr 2009, 7:38 pm

okay, fine, I'll help you. If you take the 3 to the other side, and substitute x^2 for sin²θ and x for sinθ, you will see that you have a quadratic equation. Solve for the roots and then you can get the angles.

Kangoogle
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26 Apr 2009, 8:17 pm

Lol.

gbollard
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27 Apr 2009, 12:30 am

Sorry, moved this post to Maths, Science and Technology - You'll get more answers there.

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ruveyn
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27 Apr 2009, 8:20 am

bonez wrote:

Solve the equation 8x^2 + 10x - 3 = 0

If a root of this equation lies between -1 and 1 take the arcsine (inverse sine). If neither root lies in the interval -1 to 1 then there is no such angle theta.

ruveyn

lau
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