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{12}{13}sin(θ
1

)=−
13
12

sine, left parenthesis, theta, start subscript, 1, end subscript, right parenthesis, equals, minus, start fraction, 12, divided by, 13, end fraction .
What is the value of \cos(\theta_1)cos(θ
1

)cosine, left parenthesis, theta, start subscript, 1, end subscript, right parenthesis?