Question

三角恒等式证明数学题要帮助 1 +cosx/ 1-cosx- 1-cosx/1+cos=4/sinx tanx

Answer 1

(1+cosx)/(1-cosx)-(1-cosx)/(1+cosx)

=[(1+cosx)^2-(1-cosx)^2]/[(1+cosx)(1-cosx)]

=[1+2cosx+(cosx)^2-1+2cosx-(cosx)^2]/[1-(cosx)^2]

=4cosx/(sinx)^2

=4/(sinxtanx)