Year 12s: what will be the first way you research your future options? >>

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C2 Maths help with trigonometric functions

I'm stuck on this question hopefully somone can help and give me a hint or idea on how to work it out
Sin^2(x+pi/6)=1/2 For -pi<x<pi
Should i expand the brackets?

(edited 11 years ago)

No you can't because if you did you will actually be adding up the squares of sinx and sin(pie/6). where as the question states that the the square of the sin of the angle x+pie/6 = 1/2

(edited 11 years ago)

Study Forum Helper

Pi not pie.

:angry:

:angry:

Study Forum Helper

Original post by washdog

I'm stuck on this question hopefully somone can help and give me a hint or idea on how to work it out
Sin^2(x+pie/6)=1/2 For -pie<x<pie
Should i expand the brackets?

Make a substitution

u=x+\frac{\pi}{6}

and then take the square root of each side. Don't forget the plus or minus sign.

OP

Thanks i will try this now i dont need to use this then (the unit circle rule sin(pi/6)=1/2,) and sorry for saying pie when its pi( My bad) :P

Original post by Mr M

Pi not pie.

:angry:

:angry:

\pi e

:sexface:

Study Forum Helper

Original post by Felix Felicis

\pi e

:sexface:

I actually asked one of these pie bandits if they meant

\pi e

last week. They didn't.

Original post by Mr M

I actually asked one of these pie bandits if they meant

\pi e

last week. They didn't.

Uncultured hooligans :colone:

:colone:

OP

So i now get Sin(u)= + or - root2/2 do i then go sin = + or - root2/2/X+pi/6

Study Forum Helper

Original post by washdog

So i now get Sin(u)= + or - root2/2 do i then go sin = + or - root2/2/X+pi/6

Take the arcsin and use your normal technique to find the values of u. Now subtract pi/6 from each answer to find x.

OP

Thank you very much I got x = 1/12 Pi or -5/12 pi

(edited 11 years ago)

Study Forum Helper

Original post by washdog

Thank you very much I got x = 1/12 Pi or 5/12 pi

You have lost 2 solutions. You should get 2 answers from the positive root and 2 from the negative root.

OP

Oh yh i did - 11/12 pi and - 7/12 pi :biggrin:

:biggrin:

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