SOLUTION: Hi, I am trying to complete an exam question on Further Maths Trigonometry. I have found a cosine solution of x= (2pi/3)n and the next part of the question says Use your general so

Question 827254: Hi, I am trying to complete an exam question on Further Maths Trigonometry. I have found a cosine solution of x= (2pi/3)n and the next part of the question says Use your general solution to find the smallest solution of this equation which is greater than 5pi. I don't remember covering this in class. Please would you be able to explain how to do this please
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
I have found a cosine solution of x= (2pi/3)n
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and the next part of the question says
Use your general solution to find the smallest solution of this equation which is greater than 5pi.
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PLEASE READ THIS CORRECTION TO THE ANSWER I FIRST POSTED.
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If (2/3)pi is a solution so is (4/3)pi since they have the same
cosine value of -1/2
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5pi takes you to the start of the 3rd Quadrant.
Adding 5pi you would get (5+(2/3))pi which is in the 3rd Quadrant
and has the same cosine value
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But (5-(4/3))pi would be in the 1st quadrant where the cosine is +1/2
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Ans: (5+(2/3))pi
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Cheers,
Stan H.
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