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# Urgent Help Needed, C3 maths, Trig Functions!! Watch

1. Ok, im really stuck on a certain question, and have been through the whole book and internet and cannot find anything to help me, so hopefully you can?

The question is:

Show that the equation
Sin( x + 30° ) = 2 cos ( x + 60° )
Can be written in the form 3(root)3 sin x = 1 cos x

Thanks
2. .
3. (Original post by B_9710)
.
But don't you have to keep both the cos and the sin as they are both in the final answer?
4. Just expand and rearrange to get the final expression.
5. (Original post by BAMItzCallum)
But don't you have to keep both the cos and the sin as they are both in the final answer?
I will look at it properly. Give me a minute.
6. Thanks
7. (Original post by BAMItzCallum)
Ok, im really stuck on a certain question, and have been through the whole book and internet and cannot find anything to help me, so hopefully you can?

The question is:

Show that the equation
Sin( x + 30° ) = 2 cos ( x + 60° )
Can be written in the form 3(root)3 sin x = 1 cos x

Thanks
Expand Sin (A+B) = sin A cos B + cos A sin B and cos (A+B) = cosA cos B - sin A sin B and use sin 60 = root3/2 = cos 30 and sin 30= 1/2 = cos 60. Then rearrange to get final expression.
8. (Original post by tangotangopapa2)
Just expand and rearrange to get the final expression.
I tried that, and came out with (root3)/2 sinx + 1/2 cosx = 1 cox - (root3) sinx
Which is completely wrong
9. That is not wrong take cos x terms to one side and sin x terms to other side. you get 3 root 3 sinx /2 = cos x /2. Cancel 2 to get final expression

(Original post by BAMItzCallum)
I tried that, and came out with (root3)/2 sinx + 1/2 cosx = 1 cox - (root3) sinx
Which is completely wrong
10. (Original post by tangotangopapa2)
That is not wrong take cos x terms to one side and sin x terms to other side. you get 3 root 3 sinx /2 = cos x /2. Cancel 2 to get final expression
if i put them on the same side though, i get:
(root3)/2 sinx + (root3)sinx = 1cosx + 1/2 cosx
:/
11. root3/2 + root3 is 3root3/2
You should get 1 cos x - 1/2 cos x on RHS.

(Original post by BAMItzCallum)
if i put them on the same side though, i get:
(root3)/2 sinx + (root3)sinx = 1cosx + 1/2 cosx
:/
12. (Original post by tangotangopapa2)
root3/2 + root3 is 3root3/2
You should get 1 cos x - 1/2 cos x on RHS.
Derp. Thanks so much!
13. (Original post by BAMItzCallum)
Derp. Thanks so much!
You're very welcome.

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