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# Trig equation help

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1. Please see attachment for the question. I got an answer of 0.447 but I'm not sure if that's right.
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2. (Original post by Stanspam)
Please see attachment for the question. I got an answer of 0.447 but I'm not sure if that's right.
Nope. That value is not in the given range if you're talking about the first part?
3. Let Cosx be C, let Sinx be S:

*rearrange the first equation...

26C2 = 24S2 + 8 *now replace S2 with { 1 - C2 }

rearrangeing you get an equation with just C2 which you can solve to find C { which has to be negative for the values stipulated*

once you have found C it is easy to find S ( which will be positive ).

then put these values into the second expression.
4. I think this comes out to be -4/7 but I haven't actually written anything down so that might be wrong.

(Original post by the bear)
Let Cosx be C, let Sinx be S: *rearrange the first equation... 26C2 = 24S2 + 8 *now replace S2 with { 1 - C2 } rearrangeing you get an equation with just C2 which you can solve to find C { which has to be negative for the values stipulated* once you have found C it is easy to find S ( which will be positive ). then put these values into the second expression.
Using this method.
5. (Original post by RyanW97)
I think this comes out to be -4/7 but I haven't actually written anything down so that might be wrong.

Using this method.
that is the result i got

*
6. (Original post by the bear)
that is the result i got

*
Great! At least I haven't forgotten everything from A Levels over the summer!
7. (Original post by RyanW97)
I think this comes out to be -4/7 but I haven't actually written anything down so that might be wrong.

Using this method.
Yeah it does, thanks! I just checked and I divided by the wrong number in one of the steps

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