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Trig help???

Hey guys, does anybody know how to work these out? :colondollar:

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

Reply 1

TeeEm

Original post by Rbutton

Hey guys, does anybody know how to work these out? :colondollar:

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

Reply 2

Rbutton

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 ??

Reply 3

TeeEm

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

Reply 4

Rbutton

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?

(edited 9 years ago)

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Reply 5

TeeEm

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?