Math Is Fun Forum

Peaches47

Member

Registered: 2008-02-17

Posts: 13

Trig- The Powers Of :(

Ok here we go again
I have to answer the following:

Rewrite the expression as an equivalent expression that does not contain powers of trigonometirc funcitons greater than 1.

a) cos 4x     b) cos 3x

They dont look like they have powers to me.  Guess I am real dumb when it come to these type of questions

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Struggling Middle Aged Math Student

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Trig- The Powers Of :(

I agree that they don't have powers, so the question as you stated it doesn't require anything to be done. So either:

- The book actually says cos[sup]4[/sup]x and cos[sup]3[/sup]x.

- The book actually wants you to write them as powers of sin x and cos x.

- The book is silly.

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Why did the vector cross the road?
It wanted to be normal.

Peaches47

Member

Registered: 2008-02-17

Posts: 13

Re: Trig- The Powers Of :(

Mathsyperson:  thanks for the laugh I agree the book shows examples of the Trig functions with powers .  Then ask to figure out  cos 4x however it does proved multiple choice answers of:
3-4 cos 2x + 4x / 8
or
2-4 cos 2x + 4x /8
or
3-2 cos 2x + 4x /8
or
3+4 cos 2x + 4x /8

I tired a little backwards thinking but still can't figure it out and more feed back you can add is welcome and I checked again,  unless its a typo  it does say  "cos 4x"

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Struggling Middle Aged Math Student