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1. H.
2. cos-1

sin-1

get values for cos as + or - 360

get values for sin + 180
3. For cos(x)=0.5, go up to where 0.5 is on the y-axis and then move along until you 'hit' the y=cosx graph. Then go down to the x-axis and this tells you the value.

There is more than one value though so you need to go along and down more than once.

(Original post by sdvds)
cos-1

sin-1

get values for cos as + or - 360

get values for sin + 180
No it says to use the graph.
4. (Original post by sdvds)
cos-1

sin-1

get values for cos as + or - 360

get values for sin + 180
draw horizontal lines at y =0.5 and y = 0.25 and look for intersections

EDIT
too many of us here...
I am out!
5. (Original post by iamspiderman)
How would I go about working this out? It looks very complicated..

Then look at the relevant graph ... You should be able to see repetition and symmetry in the graph ... This will give you other values of x that have the same sine or cosine
6. ..
7. (Original post by iamspiderman)
Ok well I've tried and got :

Cos^-1 (0.5) =60 degrees
(This is the first angle on x axis)

Cos x = +0.5 for all of the following angles:
60, 110, 150,210,240,300,330,390

I can see symmetry as 60 degrees is 30 degrees away from the peak (90 degrees )
That is the correct understanding of the symmetry

Consider your 150 answer ... Look at x is 150 on the graph ... Does the graph go through (150, 0.5)

Draw a line across at 0.5 look at where this crosses the cos graph ... You should only see 3 possible values
8. [.
9. (Original post by iamspiderman)
Ok so 110 is wrong and should be 120?

So the values are:
60,120,330 and 390 ?
Why do you think that 120 is correct .... Look at the graph
10. ..
11. (Original post by iamspiderman)
Yeah it is wrong I've been looking at it incorrectly
I think the values are 60, 300 and I'm not sure about the third one
Can you explain why you think 300 is a solution
12. ..
13. (Original post by iamspiderman)
I have just been taking 30 degrees away from each peak or adding 30 degrees
Have you actually been looking at the graph ... You need places that equal 0.5
14. ..
15. (Original post by iamspiderman)
By looking at the graph the second point is around 315 but when I do cos(315) it doesn't equal 0.15
Like cos(60) equals 0.15
But for the second point 279 equals 0.15
Where've you got 0.15 from - you should be looking for values that give 0.5! Or was that just a typo?
16. (Original post by iamspiderman)
By looking at the graph the second point is around 315 but when I do cos(315) it doesn't equal 0.15
Like cos(60) equals 0.15
But for the second point 279 equals 0.15
You have lost me

You know from symmetry that 315 is not right, nor is 379

Where has this 0.15 come from
17. ..

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