Gọi M = tan x − tan y thì:

2/22

Gọi \(M = \tan x - \tan y\) thì:

\(M = \tan \left( {x - y} \right).\)

\(M = \frac{{\sin \left( {x + y} \right)}}{{\cos x.\cos y}}.\)

\(M = \frac{{\sin \left( {x - y} \right)}}{{\cos x.\cos y}}.\)

\(M = \frac{{\tan x - \tan y}}{{1 + \tan x.\tan y}}.\)

Giải thích

Chọn C

Ta có: \(M = \tan x - \tan y = \frac{{\sin x}}{{\cos x}} - \frac{{\sin \,y}}{{\cos \,y}} = \frac{{\sin x\cos \,y - \cos x\sin \,y}}{{\cos x\cos \,y}}\)\( = \frac{{\sin \left( {x - y} \right)}}{{\cos x\cos \,y}}\).