- #1

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The choices are A. 2tan^2x B. 2cosx C. 2cosx-1 D. 2secx

Do I make the tan sin/cos and multiply by reciprocal of sin? I did that and end up with 1/cos + 1/cos

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- Thread starter iBankingFTW
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- #1

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The choices are A. 2tan^2x B. 2cosx C. 2cosx-1 D. 2secx

Do I make the tan sin/cos and multiply by reciprocal of sin? I did that and end up with 1/cos + 1/cos

- #2

mathman

Science Advisor

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You got it right so far. Do you know what secx is?

The choices are A. 2tan^2x B. 2cosx C. 2cosx-1 D. 2secx

Do I make the tan sin/cos and multiply by reciprocal of sin? I did that and end up with 1/cos + 1/cos

- #3

- 441

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Since tanx = (sinx/cosx) we can substitute and get:

(Sinx / cos x)/ Sin x + 1 / cos x

here we can cancel out the sin x 's and get

1 / cos x + 1 / cos x

since the denominators are the same we can add and get

2 / cos x

Now since sec x = 1 / cosx we get

2 sec x

Make sense?

- #4

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Since tanx = (sinx/cosx) we can substitute and get:

(Sinx / cos x)/ Sin x + 1 / cos x

here we can cancel out the sin x 's and get

1 / cos x + 1 / cos x

since the denominators are the same we can add and get

2 / cos x

Now since sec x = 1 / cosx we get

2 sec x

Make sense?

Yeah, thanks for that. But I thought about what mathman said and the answer was obvious, lol. Thanks a lot though for working it out.

You got it right so far. Do you know what secx is?

Yeah, so the 2(1/cosx) becomes 2secx...

That was pretty stupid, lol. Thanks though. This is a little off-topic for this thread but I really lack in courses like physics and math and I really like this forum (I'm new, lol) and what I like is how you guys don't just give an answer. You either show all the steps like Diffy did or what you did and made me think about it. :)

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- #5

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Which expression is equivalent to cos(pi + theta) (I don't know how to import the signs. and I checked the computer's character map)

So what I did was take cos(pi + theta) and put down the formula:

cos pi * cos theta - sin pi * sin theta

But I don't know what to do from there. I tried to see if I could do anything putting sin over cos but they're on opposite sides of the "-".

Choices are: A. -cos theta B. cos theta C. -sin theta D. sin theta

- #6

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you have cos(pi) and Sin(pi) in your expressions... What is the cos(pi)? sin(pi)?

- #7

- 441

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Edit:

Here is the link to the Latex tutorial:

https://www.physicsforums.com/showthread.php?t=8997

- #8

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you have cos(pi) and Sin(pi) in your expressions... What is the cos(pi)? sin(pi)?

Thanks for telling me about the symbols. That should come in handy :)

Just realized this isn't the forum for homework questions so I'm going to make a new thread in the correct section.

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