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HSC 2015 Maths Marathon (archive) (1 Viewer)

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Flop21

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Re: HSC 2015 2U Marathon

This is probably really simple, but I'm not sure how to do it.


Find all the values of 'theta' where 0* < theta < 360*, that satisfy the equation

cos(theta) - (2/5) = 0




***

Obviously you put the -2/5 on the other side, but then how do you find theta?
 

keepLooking

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Re: HSC 2015 2U Marathon




Someone teach me how to properly use LaTeX pls.

[thanks rand_althor and Drsoccerball]
 
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Drsoccerball

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Re: HSC 2015 2U Marathon

This is probably really simple, but I'm not sure how to do it.


Find all the values of 'theta' where 0* < theta < 360*, that satisfy the equation

cos(theta) - (2/5) = 0




***

Obviously you put the -2/5 on the other side, but then how do you find theta?
cos inverse both sides and one angle is the answer you see in your calculator and the other value is 360 degrees minus the first answer since cos is positive in quadrant 1 and 4
 

Drsoccerball

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Re: HSC 2015 2U Marathon







Click reply with quote and look at my code
 

rand_althor

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Re: HSC 2015 2U Marathon

Someone teach me how to properly use LaTeX pls.
Here is a more cleaner version of what you wrote:

\cos^{-1}{(\frac{2}{5})}=66.42. \, \cos{\theta}$ is positive in the 1st and 4th quadrants. $ \therefore \theta =66.42, (360-66.42)

Use dollar signs ($) to enclose text which doesn't require mathematical characters. i.e. " is positive in the 1st and 4th quadrants". "\," can be used to create a blank space. Also have a read of this: http://community.boredofstudies.org/12/mathematics/234262/short-guide-latex.html. This website is a good online editor: https://www.codecogs.com/latex/eqneditor.php
 
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keepLooking

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Re: HSC 2015 2U Marathon

Thank you so much!

I have edited my post and will read the guide before posting with LaTeX again ._.
 

Flop21

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Re: HSC 2015 2U Marathon




Someone teach me how to properly use LaTeX pls.

[thanks rand_althor and Drsoccerball]
OhhH. I was doing that but wasn't getting that answer. Maybe I had it on radian mode or something.
 

leehuan

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Re: HSC 2015 2U Marathon

Some students at my school bring two calculators into the exam room. One for degrees, one for radians. Though I never do it, it seems to work on occasion.


Now try making mathematical expressions such as

Oh, ok. Randomness time.

 

Flop21

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Re: HSC 2015 2U Marathon



So length of AO I calculated to be (square root) 2.

Now how do I find that angle? I've seen the answers but still don't understand why and how they are doing what they're doing. Could someone try and explain it like I'm stupid. Thanks.
 

Drsoccerball

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Re: HSC 2015 2U Marathon



So length of AO I calculated to be (square root) 2.

Now how do I find that angle? I've seen the answers but still don't understand why and how they are doing what they're doing. Could someone try and explain it like I'm stupid. Thanks.
Tantheta= gradient where theta is angle between line and origin
 

InteGrand

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Re: HSC 2015 2U Marathon



So length of AO I calculated to be (square root) 2.

Now how do I find that angle? I've seen the answers but still don't understand why and how they are doing what they're doing. Could someone try and explain it like I'm stupid. Thanks.
 

Flop21

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Re: HSC 2015 2U Marathon

Why does the gradient satisfy tan?? Sorry is this a property we should just know, or am I missing something?


Sorry I know I probably sound silly, but I've either missed this or forgotten it. Thanks!
 

InteGrand

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Re: HSC 2015 2U Marathon

Why does the gradient satisfy tan?? Sorry is this a property we should just know, or am I missing something?


Sorry I know I probably sound silly, but I've either missed this or forgotten it. Thanks!
 
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