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Maths C3 question

Hi,

How do you go about expressing equations as a single trigonometrical ratio? How would you do this question for example:

1/2cos(x) - (root3/2)sin(x)

Just to be clear its not the root of 1.5; its root 3 divided by 2.

Thanks a lot
Reply 1
Avatar for rampallian
rampallian
OP
9
bump
Reply 2
Avatar for B_9710
B_9710
18
Use the addition formula, cos⁡(A+B)≡cos⁡Acos⁡B−sin⁡Asin⁡B \cos (A+B)\equiv \cos A\cos B - \sin A\sin B .
Reply 3
Avatar for MiladA
MiladA
14
You use the Rcos(x+alpha) formula? So 1/2cosx -root3/2sinx = cos(x+60)
not sure how to solve without intuition
IMG_0070.jpg402.1KB
Reply 5
Avatar for MiladA
MiladA
14
IMG_20160913_191440.jpg
Original post by MiladAhmed
...


"Expand to give...."

Huh? You're not expanding anything. You're applying an identity.
Reply 7
Avatar for MiladA
MiladA
14
That's what I meant sorry. Apply the Cos(A+B) identity to Rcos(x+ alpha)

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