SOLUTION: Please help me solve this question. Solve each of the following for 0 <= theta <= 360 degrees 3sin^2 theta + 2sin theta = 0

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Question 1180791: Please help me solve this question.
Solve each of the following for 0 <= theta <= 360 degrees
3sin^2 theta + 2sin theta = 0

Found 3 solutions by MathLover1, Theo, ikleyn:
Answer by MathLover1(20850)   (Show Source): You can put this solution on YOUR website!

Solve each of the following for °


solutions:
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since given °
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°
then

°
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°
°
°
if

°
°
°
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combine solutions:

°
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°


Answer by Theo(13342)   (Show Source): You can put this solution on YOUR website!
equation is 3sin^2(theta) + 2sin(theta) = 0
factor out sin(theta) to get:
sin(theta) * (3sin(theta) + 2) = 0
this is true when sin(theta) = 0 or 3sin(theta) + 2 = 0
solve for sin(theta) to get:
sin(theta) = 0 or sin(theta) = -2/3.
the reference angle (equivalent angle in the first quadrant) will be:
theta = arcsin(0) = 0 degrees.
theta = arcsin(2/3) = 41.8103149 degrees.
note that the trig function is always positive in the first quadrant.
sin(theta) is 0 when theta = 0 or 180 degrees or 360 degrees.
sin(theta) is negative in the third and fourth quadrants.
the reference angle of 41.8103149 in the third and fourth quadrant is found as follows:
third quadrant = 41.8103149 + 180 = 221.8103149 degrees.
fourth quadrant = 360 - 41.8103149 = 318.1896851 degrees.
your angles that satisfy the equation of 3sin^2(theta) + 2sin(theta) = 0 are:
0,180,360 degrees.
221.8103149, 318.1896851 degrees.
a graph of the equation is shown below:



Answer by ikleyn(52803)   (Show Source): You can put this solution on YOUR website!
.


Comparing the solutions by  @Theo and  @MathLover1,  notice that the solution by  @Theo is correct.

The solution by  @MathLover1 is   W R O N G,   showing lack of knowledge on elementary trigonometric functions.



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