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Author Topic: c2 DOUBT  (Read 2383 times)

Offline halosh92

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Re: c2 DOUBT
« Reply #15 on: April 30, 2010, 01:06:13 pm »
another questions:

solve the following equations for thita ,in the interval 0<thita<360
(sin thita - 1)(5 cos thita + 3)


solve the following equations for x:

cos x= -0.809, -180<x<180

the x value here is= 144, how do we find the rest of the solutions using the diagram method???
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Offline astarmathsandphysics

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Re: c2 DOUBT
« Reply #16 on: April 30, 2010, 01:30:38 pm »
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Offline halosh92

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Re: c2 DOUBT
« Reply #17 on: April 30, 2010, 01:53:49 pm »
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Offline astarmathsandphysics

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Re: c2 DOUBT
« Reply #18 on: April 30, 2010, 02:26:38 pm »
Phen put each bracket=0 and solve like in the link
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Offline halosh92

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Re: c2 DOUBT
« Reply #19 on: April 30, 2010, 04:08:04 pm »
ok thx  ;D ;D ;D ;D ;D
could u please tell me how to solve such questions ?:
 find the values of thita, in the interval 0<thita<360 :
tan(45- thita)=-1

this is my method
let 45-thita = Z
but then how do i find the range for "Z" ???
thx aloooottt
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Offline Saladin

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Re: c2 DOUBT
« Reply #20 on: April 30, 2010, 04:27:35 pm »
tan(45-x)=-1

Therefore, arctan(-1) = -45

This can also mean that arctan(-1) is 135 and 315.

Thus, the only answer that is between 0 and 360 is 90.
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Offline Saladin

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Re: c2 DOUBT
« Reply #21 on: April 30, 2010, 04:30:51 pm »
Please note that arctan is just tan^-1
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Offline halosh92

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Re: c2 DOUBT
« Reply #22 on: April 30, 2010, 05:13:59 pm »
Quote from: Mr. Enigmatic on April 30, 2010, 04:30:51 pm
Please note that arctan is just tan^-1

its 90 and 270 actually
thx but  ;)
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Offline halosh92

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Re: c2 DOUBT
« Reply #23 on: April 30, 2010, 05:46:47 pm »
cos(50 + 2 thita)=-1

??? how to find thita?
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Offline Saladin

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Re: c2 DOUBT
« Reply #24 on: April 30, 2010, 06:18:41 pm »
The answer is 65 and 245.

Work out the value of cos(x)=-1

Then you get 180.

So, 2x+50=180

Now you get 65

Now, just do 180+65, because you want a negative value. Cos will be negative in this quadrant.

And u get 245
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