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Solve -2/3cot(2x)=0 Help

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Reply 20
Avatar for Zacken
Zacken
22
Original post by Alisahussain1
im sorry but that makes no sense to me at all :s-smilie: but as long as you understand it thats fine with me


What don't you understand?
Original post by Zacken
What don't you understand?


wait i think i know what youre talking about!!
but i dont get the exact same answers as i did before because i get pi/4 and 7pi/4??
Reply 22
Avatar for Zacken
Zacken
22
Original post by Alisahussain1
wait i think i know what youre talking about!!
but i dont get the exact same answers as i did before because i get pi/4 and 7pi/4??


How do you get that?

cos 2x = 0 when 2x = pi/2 or 3pi/2

So x = pi/4 or 3pi/4.
Original post by Zacken
What don't you understand?


i got

cos2x=0
2cos^2x-1=0
cos^2x=1/2
cosx= sqrt(1/2)
cosx=plus or minus 1/2
x=pi/4 and 7pi/4
Original post by Zacken
How do you get that?

cos 2x = 0 when 2x = pi/2 or 3pi/2

So x = pi/4 or 3pi/4.


ohhh you just substituted random numbers in until you got 0, i see
Reply 25
Avatar for Zacken
Zacken
22
Original post by Alisahussain1
ohhh you just substituted random numbers in until you got 0, i see


...what? No, not at all...
Original post by Zacken
...what? No, not at all...


LOL dont worry, as long as i got it right im not to bothered haha
Reply 27
Avatar for Zacken
Zacken
22
Original post by Alisahussain1
LOL dont worry, as long as i got it right im not to bothered haha


But this is a worrying gap in your knowledge, surely?

Set y = 2x

then you have cos y = 0

Solve cos y = 0.

Then y = pi/2, 3pi/2, yes?

Now replace y with 2x again.

So 2x = pi/2 or 2x = 3pi/2, yes?

Now solve for x by dividing both sides.
Original post by Zacken
But this is a worrying gap in your knowledge, surely?

Set y = 2x

then you have cos y = 0

Solve cos y = 0.

Then y = pi/2, 3pi/2, yes?

Now replace y with 2x again.

So 2x = pi/2 or 2x = 3pi/2, yes?

Now solve for x by dividing both sides.


ohhhh i get itt!!! thank you! i just made a calculation error when i was putting the numbers in the calculator lol
(edited 7 years ago)
Reply 29
Avatar for Zacken
Zacken
22
Original post by Alisahussain1
ohhhh i get itt!!! thank you! i just made a calculation error when i was putting the numbers in the calculator lol


Cool.

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