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# C3 chapter 7 trigonometry watch

1. Please see photo. Why can't the answer also be tan(5pi/4 + X) and so on as tan is a recurring cycle graph thingy? The answer in the book is only pi/4 and there was no range given in the question?
Same for 12d

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2. (Original post by anoymous1111)
Please see photo. Why can't the answer also be tan(5pi/4 + X) and so on as tan is a recurring cycle graph thingy? The answer in the book is only pi/4 and there was no range given in the question?
Same for 12d

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nobody seems to want to help because of the sideways picture....
3. (Original post by TeeEm)
nobody seems to want to help because of the sideways picture....
Are you serious?

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4. (Original post by anoymous1111)
Are you serious?

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looks that way
5. (Original post by anoymous1111)
Please see photo. Why can't the answer also be tan(5pi/4 + X) and so on as tan is a recurring cycle graph thingy? The answer in the book is only pi/4 and there was no range given in the question?
Same for 12d

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The answer CAN be tan(5pi/4 + X). But there's no point in writing this, because tan(5pi/4 + X) = tan(pi/4 + X).

The question is just asking you to write the original expression as a single trig expression. It's not saying "there is only one way to do this", but most people would choose the simplest possible form.
6. (Original post by davros)
The answer CAN be tan(5pi/4 + X). But there's no point in writing this, because tan(5pi/4 + X) = tan(pi/4 + X).

The question is just asking you to write the original expression as a single trig expression. It's not saying "there is only one way to do this", but most people would choose the simplest possible form.
Ok thank you!

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7. Hey I was doing the same question so you know for 12D the question at the bottom. I know that youre answer is right but how did you get (Sinθ+Pi/4). Why isnt it (Sinθ-Pi/4).
Thanks!
8. (Original post by Lilly1234567890)
Hey I was doing the same question so you know for 12D the question at the bottom. I know that youre answer is right but how did you get (Sinθ+Pi/4). Why isnt it (Sinθ-Pi/4).
Thanks!
If you look at the double angle formula, sin(A+B) =sinAcosB + sinBcosA.
In this case you do have sinA + cosA in the brackets therefore it must be sin(A+B).
If it was sin(A-B) then you would have sinA-cosA in the brackets
Not great at explaining but hope that helps

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Updated: November 5, 2015
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