How do you evaluate sec^2(18) - tan^2(18)? Trigonometry Right Triangles Trigonometric Functions of Any Angle 1 Answer Anjali G May 21, 2018 sec^2(18) - tan^2(18) = 1/cos^2(18) - sin^2(18)/cos^2(18) = (1-sin^2(18))/cos^2(18) = cos^2(18)/cos^2(18) = 1 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 11484 views around the world You can reuse this answer Creative Commons License