Question

Tính

\(tan^240^o.sin^250^o-3+\left(1-sin40^o\right).\left(1+sin40^o\right)\)

Answer 1

\(=\dfrac{\sin^240^0}{\cos^240^0}\cdot\cos^240^0-3+1-\sin^240^0=\sin^240^0-\sin^240^0-2=-2\)