Answer:
cos(θ) = (-√5)/3
Step-by-step explanation:
The relation between sine and cosine is ...
cos(x) = ±√(1 -sin(x)²)
Here, that means ...
cos(θ) = ±√(1 -(2/3)² = ±√(5/9)
The tangent is negative where the signs of sine and cosine are different. We want the cosine to have a negative sign, so we have ...
cos(θ) = -(√5)/3
