(secα)^2=2(secβ)^2如何得到1-(sinβ)^2=2[1-(sinα)^2].
问题描述:
(secα)^2=2(secβ)^2如何得到1-(sinβ)^2=2[1-(sinα)^2].
答
(secα)^2=2(secβ)^2
1/(cos α)^2=2/(cos β)^2
2(cos α)^2=(cos β)^2
2[1-(sinα)^2]=1-(sinβ)^2