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# Urgent help please Trigonometry a Level watch

Thank you
cos^4 theta + 2sin^2 theta + sin^4 theta
So far I've done:
Cos^2 theta (cos^2 theta +1) + sin^2 theta ( 2+ sin^2)
(Cos ^2 theta)( sin^2 theta) = (2+sin^2)(cos^2 theta +1)
Cos^2 sin^2 theta= 2cos^2 theta + 2 + sin^2 cos ^2 theta + sin^2
Cos^2sin^2 theta= 2cos^4 2theta + sin^4 +2
Cos^2 2 theta + sin^2 theta +2
Cos^2 2 theta + sin^2 theta + 2 = 1
2. Can you explain your first line? There's issues beyond that but your initial assertion (?) of is incorrect. Perhaps you added a +1 in the first brackets by mistake? I'm not sure where you're going with the rest.

Spoiler:
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also pings to move this to the correct section Sonechka Lemur14

3. Can't move on the app, will move when I get home
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4. (Original post by _gcx)
Can you explain your first line? There's issues beyond that but your initial assertion (?) of is incorrect. Perhaps you added a +1 in the first brackets by mistake? I'm not sure where you're going with the rest.

Spoiler:
Show

also pings to move this to the correct section Sonechka Lemur14

Oops I think I wrote it wrong
The question is:
Simplify the following expressions:
Cos^4 theta + 2sin^2 theta cos^2 theta + sin^4 theta
5. (Original post by Musicanor)
Oops I think I wrote it wrong
The question is:
Simplify the following expressions:
Cos^4 theta + 2sin^2 theta cos^2 theta + sin^4 theta
In that case your final answer is correct, but you have some mistakes in your working. (I'm not sure how you reached your conclusion from your last few lines. If you graph you'll see that it's neither constant nor equal to 1) It's easier to factorise. We have . Does this look familiar?
6. (Original post by _gcx)
In that case your final answer is correct, but you have some mistakes in your working. (I'm not sure how you reached your conclusion from your last few lines. If you graph you'll see that it's neither constant nor equal to 1) It's easier to factorise. We have . Does this look familiar?
mmmm...
cos 2 θ − sin 2 θ = 1 − 2 sin 2 θ ????
7. (Original post by Musicanor)
mmmm...
cos 2 θ − sin 2 θ = 1 − 2 sin 2 θ ????
No, that's not true, (that is, it isn't an identity) unless you mean etc.

Try expanding . What do you see?
8. (Original post by _gcx)
No, that's not true, (that is, it isn't an identity) unless you mean etc.

Try expanding . What do you see?
X^4 +y^4 + x^4y^4
9. (Original post by Musicanor)
X^4 +y^4 + x^4y^4
Or is it 2x^4 +2x^4 2y^4 +2y^4
10. (Original post by Musicanor)
X^4 +y^4 + x^4y^4
You should be comfortable with this,

You have
11. (Original post by _gcx)
You should be comfortable with this,

You have
Thanks.

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