Question

Cho tan 2 =1/3. Tính cos2- sin2 / cos2 - sin2

Answer 1

Ta có 

tan 2 = \(\dfrac{sin2}{cos2}\)

ma tan 2 = \(\dfrac{1}{3}\)

=> sin 2 = 1; cos 2 = 3

\(\dfrac{cos2-sin2}{cos2-sin2}=\dfrac{3-1}{3-1}=\dfrac{2}{2}=1\)