Question

(secα)^2=2(secβ)^2如何得到1-(sinβ)^2=2[1-(sinα)^2].

Answer 1

(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