- #1

- 655

- 0

cosec2x = 3/2

sin2x = 2/3

2x = 41.8...

this means 41.8.. / 2 AND (180 - 41.8...) / 2

now there is 2 other angle that make this true. How do I find them.

Thanks :)

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- Thread starter thomas49th
- Start date

- #1

- 655

- 0

cosec2x = 3/2

sin2x = 2/3

2x = 41.8...

this means 41.8.. / 2 AND (180 - 41.8...) / 2

now there is 2 other angle that make this true. How do I find them.

Thanks :)

- #2

HallsofIvy

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Those are the

- #3

- 655

- 0

Errrrr apparently according to here

http://eiewebvip.edexcel.org.uk/Reports/Confidential Documents/0706/6665_01_rms_20070815.pdf

are x = 20.9°, 69.1°, 200.9°, 249.1° (1 d.p.)

im not sure how they got the last 3. They seem to have done

90 - 20.9

180 + 20.9

270- 20.9

can you explain why

Thanks :)

http://eiewebvip.edexcel.org.uk/Reports/Confidential Documents/0706/6665_01_rms_20070815.pdf

are x = 20.9°, 69.1°, 200.9°, 249.1° (1 d.p.)

im not sure how they got the last 3. They seem to have done

90 - 20.9

180 + 20.9

270- 20.9

can you explain why

Thanks :)

Last edited by a moderator:

- #4

nicksauce

Science Advisor

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So we want values for 0 < u < 720 where sinu = 2/3

They are u = 41.8, 138.2, 401.8, 498.2 (The last two are from adding 360 to the previous two).

Then divide by two to get the values of x.

- #5

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[tex]2 \csc (2x) = 3[/tex] What does it mean to take the trig function of any 2x, 3x, or nx. In other equations when you solve for simply x, you are left with two solutions because the graph fluctuates once in 2 pi in which the solutions fall in two quadrants(like cos in 1 and 4 and sin in 1 and 2). While here, we are given 2x meaning the graph itself has two cycles in 2 Pi. Meaning, there are a total of four answers(thats if you are looking for [tex]0\leq 0 < 2\pi[/tex], not that i did not set it equal to 2pi).Graph it the equation and you will see what I mean by two cycles in 2 pi.

If you understand this, you are pretty much set with finding many trig. solutions as this is a very important point to note about trig. functions.

If you understand this, you are pretty much set with finding many trig. solutions as this is a very important point to note about trig. functions.

Last edited:

- #6

HallsofIvy

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