# Trig help???

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#1
Hey guys, does anybody know how to work these out? 1) sin3x=3sinx-4sin3x
Given sin3x=(√3)/4, find the exact value of sin3x

2)Given cosec2x-cot2x=tanx and tan15=2-√3
Solve cosec4x-cot4x=1 for 0 < x < 360
0
5 years ago
#2
(Original post by Rbutton)
Hey guys, does anybody know how to work these out? 1) sin3x=3sinx-4sin3x
Given sin3x=(√3)/4, find the exact value of sin3x

2)Given cosec2x-cot2x=tanx and tan15=2-√3
Solve cosec4x-cot4x=1 for 0 < x < 360
for the first write sin(3x) as sin(2x+x), then use compound angle followed by double angle
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#3
(Original post by TeeEm)
for the first write sin(3x) as sin(2x+x), then use compound angle followed by double angle
That gives sin3x=3sinx-4sin3x ???Then the question is to find sin3x when sin3x=(√3)/4 ... Why isn't the exact value of sin3x just sin3x=(√3)/4 ??
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5 years ago
#4
(Original post by Rbutton)
That gives sin3x=3sinx-4sin3x ???Then the question is to find sin3x when sin3x=(√3)/4 ... Why isn't the exact value of sin3x just sin3x=(√3)/4 ??
either there is a typo in what you are typing or something wrong.

Is this the first question in Jan 2007 C3?

then it should read sinx = blah root blah and not sin3x
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#5
(Original post by TeeEm)
either there is a typo in what you are typing or something wrong.

Is this the first question in Jan 2007 C3?

then it should read sinx = blah root blah and not sin3x
I did 1a) the way you described, but its 1b) that's confusing me. Assuming its the question you're talking about, its probably safe to say he meant to write sinx?? If so do you just divide (√3)/4 by three or is it more complex than that?
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5 years ago
#6
(Original post by Rbutton)
I did 1a) the way you described, but its 1b) that's confusing me. Assuming its the question you're talking about, its probably say to say he meant to write sinx?? If so do you just divide (√3)/4 by three or is it more complex than that?

THIS IS A TYPO (see my previous post)

see the actual exam where the question came from.

C3, January 2007.pdf

does this explain?
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#7
(Original post by TeeEm)
THIS IS A TYPO (see my previous post)

see the actual exam where the question came from.

C3, January 2007.pdf

does this explain?

That's what I meant when I said its probably safe to say he meant to write sinx...
Yeah, I think I get it now, thank you
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5 years ago
#8
(Original post by Rbutton)
That's what I meant when I said its probably safe to say he meant to write sinx...
Yeah, I think I get it now, thank you
pleasure
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