The angle \theta_1θ 1 theta, start subscript, 1, end subscript is located in Quadrant \text{III}IIIstart text, I, I, I, end text, and \sin(\theta_1)=-\dfrac{\sqrt{3}}{2} sin(θ 1 )=− 2 3 sine, left parenthesis, theta, start subscript, 1, end subscript, right parenthesis, equals, minus, start fraction, square root of, 3, end square root, divided by, 2, end fraction . What is the value of \cos(\theta_1)cos(θ 1 )cosine, left parenthesis, theta, start subscript, 1, end subscript, right parenthesis? Express your answer exactly. \cos(\theta_1)=cos(θ 1 )=cosine, left parenthesis, theta, start subscript, 1, end subscript, right parenthesis, equals