kaylala
Trigonometric Equation
2tan^2A + 3secA = 0
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kaylala
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@hartnn
Another one please
hartnn
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which pythagorean identities do you know ?
kaylala
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I've bee through all except for the half identities
kaylala
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@hartnn
hartnn
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so which identity relates tan^2 A and sec^2 A ?
kaylala
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Sin?
kaylala
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I mean cos?
hartnn
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ever sen this ?
\(\\tan^2 A =sec^2A-1\)
?
use it here
kaylala
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Yes. I'm familiar with that
Wait. Let me try
kaylala
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I got 2x^2+3x-2
Is it right?
So i may move on
hartnn
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yes,
that = 0
remember its an equation, not an expression
kaylala
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Oh right
kaylala
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How'll this be nothing will equal to 3x?
kaylala
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@hartnn ^
hartnn
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what ? i didn't get your question...
hartnn
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2x^2+3x-2 = 0
x= .....
x=....
kaylala
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Oh sorry
What i meant was what should i do next?
How do i find x?
I cant use the FOIL method.
hartnn
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factor method.
2 numbers with sum = +3 and product = -4
kaylala
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Got it
Wait
kaylala
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Sec = 1/2
Sec={no solution
Sec=-2
No solution
?????
I dont know
Hpw's this?
@hartnn
hartnn
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sec A can be -2
kaylala
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I dont see any negative 2 in the graph list
Sec A =-2
hartnn
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sec A = -2
secA = 1/cos A
cos A = -1/2
when ?
kaylala
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I dont see any cos A =-1/2
There is only cos A=1/2
kaylala
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Or did i get it wrong?
kaylala
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@hartnn ^
hartnn
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how about angles 120 and 210 ?
kaylala
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Where did you get that.
Those arent in the graph that was given to us
kaylala
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Oh i see now
So will the answer for secA=-2 or cosA=-1/2 be:
A={120,210}
kaylala
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Is that it already?
How about sec=1/2? Does it really have no solution?
@hartnn
hartnn
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yes. in the range 0 to 360.
range of sec function does not include values between -1 and 1
so, sec A = 1/2 will have no solution,
(in the same way cos A = 2 have no solution)
kaylala
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Okay thanks again
hartnn
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welcome ^_^