How do you find the exact value of cos pi/6 cos pi/3 - sin pi/6 sin pi/3? Trigonometry Right Triangles Trigonometric Functions of Any Angle 1 Answer Ratnaker Mehta Aug 10, 2018 0.0. Explanation: Recall that, cosxcosy-sinxsiny=cos(x+y)cosxcosy−sinxsiny=cos(x+y). Hence, with x=pi/6 and y=pi/3x=π6andy=π3, we have, cos(pi/6)cos(pi/3)-sin(pi6)sin(pi/3)cos(π6)cos(π3)−sin(π6)sin(π3), =cos(pi/6+pi/3)=cos(π6+π3), =cos(pi/6+2pi/6)=cos(π6+2π6), =cos(3pi/6)=cos(3π6), =cos(pi/2)=cos(π2), =0=0. 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^\circ140∘? How do you find the value of cot 300^@cot300∘? What is the value of sin -45^@sin−45∘? How do you find the trigonometric functions of values that are greater than 360^@360∘? How do you use the reference angles to find sin210cos330-tan 135sin210cos330−tan135? How do you know if sin 30 = sin 150sin30=sin150? How do you show that (costheta)(sectheta) = 1(cosθ)(secθ)=1 if theta=pi/4θ=π4? See all questions in Trigonometric Functions of Any Angle Impact of this question 6657 views around the world You can reuse this answer Creative Commons License