Wednesday, July 17, 2013

How to solve this trigonometric equations?tan 2x cot x I need to factor this in order to sove for 0

tan2x*cotx - 3 = 0


We know
that: tan2x = sin2x/cos2x and cotx = cosx/sinx


==>
sin2x/cos2x *cosx/sinx = 3


Now we know that sin2x =
2sinx*cosx


==> 2sinxcosx/cos2x * cosx/sinx =
3


Reduce sinx:


==>
2cos^2 x/ cos2x = 3


Now we know that cos2x = 2cos^2
x-1


==> 2cos^2 x/(2cos^2 x -1) =
3


==> 2cos^2 x = 3(2cos^2 x
-1)


==> 2cos^2 x = 6cos^2 x -
3


==> -4cos^2 x=
-3


==> 4cos^2 x =
3


==> cos^2 x =
3/4


==> cosx = +-sqrt3/
2


==> x = pi/6, 5pi/6, 7pi/6, and
11pi/6

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