What is the reference angle of sin(-45)? Trigonometry Right Triangles Trigonometric Functions of Any Angle 1 Answer Jim H Apr 26, 2015 Assuming you mean #-45# radians, the reference angle is #14pi - 45# #45 -: 2 pi ~~ 7.16# and #14 pi ~~ 43.98# So, to get #-45# that only leaves about #-1.02# which is a 4th quadrant angle with reference angle #1.02#. The exact value is #14pi - 45# 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 1941 views around the world You can reuse this answer Creative Commons License