1、cos的4次方α-sin的4次方α=多少?2、tanα=2,则tan（π/4+α）等于做少?

1.利用两数平方差的因式分解公式[a^2-b^2=(a+b)(a-b)],先把四次方化为二次方,再按三角函数化简即可.cin^4α-sin^4α=(con^2α)^2-(sin^2α)^2=(con^2α+sin^2α)(con^2α-sin^2α)因sin^2α+con^2α=1,con^2α-sin^2...