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Differentiation proving question!

Hi everyone,
I'm stuck on this problem for differentiation.


Here's what I've done so far. I have no idea how to go on...

Screen shot 2014-10-23 at 2.46.31 PM.png198.7KB
Screen shot 2014-10-23 at 2.36.45 PM.png12.9KB
Original post by Fintastic
...


Good so far.

Look at what you're aiming for. Format is tan(A-B)

Does that give you a hint on how ot proceed?
Reply 2
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Fintastic
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Original post by ghostwalker
Good so far.

Look at what you're aiming for. Format is tan(A-B)

Does that give you a hint on how ot proceed?


Er so far all I can think about is breaking it up .

Sin t / ( sin t + cos t ) - cos t /( sin t + cos t)
Then I'll change to tangent from there.
What about the π/4 ? Just multiply with like sin π/4 / cos π/4 cos t ?
Original post by Fintastic
...


OK. Don't break it up.

If you expand tan (t-pi/4) what do you get? And tan(pi/4) = ....

Now compare that to what you have already.
(edited 9 years ago)
Reply 4
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Fintastic
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Original post by ghostwalker
OK. Don't break it up.

If you expand tan (t-pi/4) what do you get? And tan(pi/4) = ....

Now compare that to what you have already.


tan t - tan π/4 / ( 1 + tan t tan π/ 4 )

tan π/ 4 = 1

... I think I get it. So if there's a (1) I can change it to tan π/ 4?

Original post by Fintastic


tan t - tan π/4 / ( 1 + tan t tan π/ 4 )

tan π/ 4 = 1

... I think I get it. So if there's a (1) I can change it to tan π/ 4?



Yep.
Reply 6
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Fintastic
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Original post by ghostwalker
Yep.


Ohhhh. Okay thank you!
Original post by Fintastic
Ohhhh. Okay thank you!


You're welcome.

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