Trig help! (1 Viewer)

[SGSII]

Hey

Can you help solve this question:



I know you have to draw a triangle and i did a)

But how do i do it for 2 thetas and 4 thetas?

Please provide steps.

Thanks

 

[J-Wang]

do u know what the answers say? i would just like to check b4 i post

 

[Peeik]

Although this is posted in the 'mathematics' section....I can only think of doing this question using results learnt in 3u. You are a 3U student according to your sig yeah? If so then:

Sin 2θ = 2sinθcosθ

Then use the triangle you found in the first part and sub it in above to get your answer.

Sin4θ= 2 sin2θcos2θ
= 4sinθcosθ(cos^2θ-sin^2θ)

Then sub the values in to the corresponding parts.

Damn....i should learn to use latex.

 

[SGSII]

do u know what the answers say? i would just like to check b4 i post

The answer is:

 

[SGSII]

Although this is posted in the 'mathematics' section....I can only think of doing this question using results learnt in 3u. You are a 3U student according to your sig yeah?

Yeapps

 

[SGSII]

Although this is posted in the 'mathematics' section....I can only think of doing this question using results learnt in 3u. You are a 3U student according to your sig yeah? If so then:

Sin 2θ = 2sinθcosθ

Then use the triangle you found in the first part and sub it in above to get your answer.

Sin4θ= 2 sin2θcos2θ
= 2sinθcosθ(cos^2θ-sin^2θ)

Then sub the values in to the corresponding parts.

Damn....i should learn to use latex.

Ahhs okays

Thank you soo much !

 

[Timske]

<a href="http://www.codecogs.com/eqnedit.php?latex=sin2\theta=2\sin\theta\cos\theta" target="_blank"><img src="http://latex.codecogs.com/gif.latex?sin2\theta=2\sin\theta\cos\theta" title="sin2\theta=2\sin\theta\cos\theta" /></a>

This should help

 

[J-Wang]

well the answer to c is found by expanding sin2x=2sinxcosx
and the answer to e is found by having sin4x=sin(2x+2x)=sin2xcos2x+sin2xcos2x
NB cos2x=cos^2x-sin^2x

 

[J-Wang]

should be easy from there

 

[Peeik]

Ahhs okays

Thank you soo much !

Um, i made a little mistake.....look at my edited post above.....i put a 2 when its meant to be a 4. I just did it on paper and you should get the right answer.

 

[SGSII]

Um, i made a little mistake.....look at my edited post above.....i put a 2 when its meant to be a 4. I just did it on paper and you should get the right answer.

No biggie
I managed. Thanks !