tan θ=2 sin θ

Solve each equation on the interval 0≤θ<2pi

tan θ=2 sin θ

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Cindy S. | A Heart for MathA Heart for Math

tan x = 2 sin x I am going to use x since it is quicker for me to type.

tan x - 2 sin x = 0 move everything over to one side

(sin x)/(cos x) - 2 sin x = 0 write tangent in terms of sines and cosines

sin x (1/cos x - 2) = 0 factor out sine

sin x = 0 or 1/cos x - 2 = 0 set each factor equal to zero

sin x = 0 what angles give you a sine value of zero? x = n * pi where n is an integer.

We are looking for angles in [0, 2pi) so 0*pi and 1*pi are the only angles in that interval. So, 0 and pi are two of our solutions.

1/cos x - 2 = 0 cos x = 1/2 your reference angle is pi/3

cosine is positive in quadrants 1 and 4, so pi/3 and 5*pi/3 are the angles in our interval.

x = 0, pi, pi/3 and 5*pi/3 are the solutions.

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