Question

已知tan(pie/4+x)=-2求cot2x

Answer 1

pie=p

tan(p/4+x)=(tanp/4+tanx)/(1-tanp/4tanx)=(1+tanx)/(1-tanx)=-2

tanx=3

所以,cot2x=(1-tan^2x)/(2tanx)=(-8)/(6)=-4/3