find the value of cosine function tan θ = -2/3 and angle θ lies in the second quadrant, what is the value of cos θ
tan x = -2/3
We need to find cosx such that x is in the second quadrant.
We know that:
sinx/cosx = tanx = -2/3
==> sinx =...
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Since the angle θ is in the second quadrant, then the value of the cosine function is negative.
(cos θ)^2 = 1/[1 + (tan θ)^2]
cos θ = 1/sqrt[1 + (tan θ)^2]
tan θ = -2/3 => (tan θ)^2 = 4/9
cos θ = 1/sqrt(1 + 4/9)
cos θ = 3/sqrt13
cos θ = 3*sqrt13/13