How do you evaluate cos (-30)? Trigonometry Right Triangles Trigonometric Functions of Any Angle 1 Answer Monzur R. Mar 31, 2018 cos(-30)=1/2sqrt3 Explanation: For any angle, cosvartheta=cos(-vartheta) So cos(-30)=cos30=cos(1/6pi)=sqrt3/2=1/2sqrt3 Answer link Related questions How do you find the trigonometric functions of any angle? What is the reference angle? How do you use the ordered pairs on a unit circle to evaluate a trigonometric function of any angle? What is the reference angle for 140^\circ? How do you find the value of cot 300^@? What is the value of sin -45^@? How do you find the trigonometric functions of values that are greater than 360^@? How do you use the reference angles to find sin210cos330-tan 135? How do you know if sin 30 = sin 150? How do you show that (costheta)(sectheta) = 1 if theta=pi/4? See all questions in Trigonometric Functions of Any Angle Impact of this question 5439 views around the world You can reuse this answer Creative Commons License