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# C2 trig identities watch

1. Simplify:

cos4x + 2sin2xcos2x + sin4x
2. try factorise, btw i think u may have made a typo on the second term the cos^4x bit
3. (Original post by cj_134)
try factorise, btw i think u may have made a typo on the second term the cos^4x bit
thx..yh i changed it nw..
i tried factorising but i dnt get it!!
4. (Original post by tfdes)
thx..yh i changed it nw..
i tried factorising but i dnt get it!!
Think about what (x+y)^2 comes out as and try to relate it to this question.
5. (Original post by tfdes)
thx..yh i changed it nw..
i tried factorising but i dnt get it!!
try let x = cos^2 theta and y = sin^2 theta , you get
x^2 +2xy + y^2
factors as
(x+y)^2
put x and y back in
(cos^2 theta + sin^2 theta)^2
im sure u can take it from here
6. (Original post by cj_134)
try let x = cos^2 theta and y = sin^2 theta , you get
x^2 +2xy + y^2
factors as
(x+y)^2
put x and y back in
(cos^2 theta + sin^2 theta)^2
im sure u can take it from here
okk..i got it so far..but hw do i end it? final answer is 1..hw do i get tht?!?
7. it looks like a quadratic - factorise into (sin^2 x + cos^2 x) (sin^2 x + cos^2 x) (ie, it's squared)

also sin^2 x + cos^2 x = 1 (pythagoras)

so it's effectively 1 squared = 1 hope it helps!
8. (Original post by macccj)
it looks like a quadratic - factorise into (sin^2 x + cos^2 x) (sin^2 x + cos^2 x) (ie, it's squared)

also sin^2 x + cos^2 x = 1 (pythagoras)

so it's effectively 1 squared = 1 hope it helps!
pythagoras?? what?!? omg..im reali gna fail dis c2 exam..
9. (Original post by macccj)
it looks like a quadratic - factorise into (sin^2 x + cos^2 x) (sin^2 x + cos^2 x) (ie, it's squared)

also sin^2 x + cos^2 x = 1 (pythagoras)

so it's effectively 1 squared = 1 hope it helps!
ohhhhhhhhhhhh okkk i got ittttt thxxxxxxxxxxx
10. (Original post by tfdes)
Simplify:

cos4x + 2sin2xcos2x + sin4x
nty
11. hahaha, sure? it's just one of those funny rule things
12. also, how do you make the square-power appear there, instead of typing ^2..?
13. (Original post by macccj)
also, how do you make the square-power appear there, instead of typing ^2..?
u type [ sup ] x [ / sup ]
and for A2 u do [ sub ] x [ / sub ]
(wit no spaces in bwtween)
14. (Original post by macccj)
also, how do you make the square-power appear there, instead of typing ^2..?

(Original post by tfdes)
u type [ sup ] x [ / sup ]
and for A2 u do [ sub ] x [ / sub ]
(wit no spaces in bwtween)
Alternatively, use LaTeX (see post here: http://www.thestudentroom.co.uk/wiki/LaTex ) which gives even neater results.

e.g.
15. Thank you!!
16. (Original post by tfdes)
Simplify:

cos4x + 2sin2xcos2x + sin4x
cosx=u, sinx=v

v^2+2uv+u^2 is obviously (v+u)^2

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