Given #theta = (19pi) / 6# how do you find #costheta#? Trigonometry Right Triangles Trigonometric Functions of Any Angle 1 Answer Nghi N. Jun 23, 2015 Find #cos ((19pi)/6)# Explanation: #cos ((19pi)/6) = cos ((7pi)/6 + 2pi)# = #cos (pi/6 + pi) #= #= -cos (pi/6) = (-sqrt3)/2# 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 1319 views around the world You can reuse this answer Creative Commons License