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# 2cosfeta+sinfeta=1 watch

1. how do i solve this equation? i tried to get tan already?
2. You'd have to combine the 2 trig functions using the R formula if you want.
3. = theta =/= feta

Almost as bad as that other thread where was said to be lavender
4. (Original post by thekidwhogames)
You'd have to combine the 2 trig functions using the R formula if you want.
More commonly known as the Harmonic Addition Theorem.
5. (Original post by MR1999)
More commonly known as the Harmonic Addition Theorem.
Yes that's true but most A level students remember it by 'R formulae' as I believe that's what it's often referred to as.
6. (Original post by thekidwhogames)
Yes that's true but most A level students remember it by 'R formulae' as I believe that's what it's often referred to as.
yhh i have actually been taught this! how would i apply it here?
7. (Original post by mansnothot)
yhh i have actually been taught this! how would i apply it here?
Use it to combine the 2 trig functions. Do you know the identity?
8. (Original post by thekidwhogames)
Use it to combine the 2 trig functions. Do you know the identity?
yes its like R(theta+alpha) or Rcos(theta+alpha) right?
9. (Original post by mansnothot)
yes its like R(theta+alpha) or Rcos(theta+alpha) right?
Your original problem was. 2cos(x) + sin(x) = 1. R = root of 2^2 + 1^2 meaning R=root 5. Alpha = arc tan (1/2). Plug this into your calculator. If you want it into a single cosine function: AcosX + BsinX = Rcos(X-alpha).

2cosfeta+sinfeta=1 watched
10. (Original post by thekidwhogames)
Your original problem was. 2cos(x) + sin(x) = 1. R = root of 2^2 + 1^2 meaning R=root 5. Alpha = arc tan (1/2). Plug this into your calculator. If you want it into a single cosine function: AcosX + BsinX = Rcos(X-alpha).

2cosfeta+sinfeta=1 watched
arc tan (1/2)=0.464.

The final 2 answers are theta= 1.57 or 5.64 so how would i get these?
11. (Original post by mansnothot)
arc tan (1/2)=0.464.

The final 2 answers are theta= 1.57 or 5.64 so how would i get these?
So the new equation is root 5 cos (x-0.464) =1
cos(x-0.464) = 1 / root 5

Now you're solving a simple trig equation. You can use CAST or the graph but essentially:

x-0.464 = 1.107... or 5.176

so x = 1.57 or 5.64 (2dp).
12. (Original post by thekidwhogames)
So the new equation is root 5 cos (x-0.464) =1
cos(x-0.464) = 1 / root 5

Now you're solving a simple trig equation. You can use CAST or the graph but essentially:

x-0.464 = 1.107... or 5.176

so x = 1.57 or 5.64 (2dp).
so i got 1.57. how would i use the graph to get the other value? i know u have to look for the value of x and take it away from 2pi or something but i dont get the answer.
13. feta
14. Feta cheese

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