Question

given that cotθ = 3, cos θ<0 find the exact value of cos θ/2

Answer 1

I know to use the half angle for cosine but I don't know what to do with the cotangent.

Answer 2

cotθ = 3 cos θ<0
?

Answer 3

cotθ =3 and cos θ<0

Answer 4

the angle is the the 3rd quadrant where tan is positive and cas is negative

If cot = 3 then tan = 1/3

draw the diagram and find the hypotenuse using Pythagoras' theorem



\[\cos \theta = -\frac{3}{\sqrt{10}}\]