已知sinα=2sinβ,tanα=3tanβ,求αcos^2的值① 已知sin =2sinβ，tan =3tanβ，求的值._其他解答

已知sinα=2sinβ,tanα=3tanβ,求αcos^2的值
① 已知sin =2sinβ，tan =3tanβ，求的值.

人气：279 ℃　时间：2019-12-09 21:55:06

解答

sinα=2sinβsin^2β=sin^2α/4=(1-cos^2α）/4cos^2β=1-sin^2β=1-(1-cos^2α）/4=(3+cos^2α）/4tanα=3tanβ(sinα/cosα)^2=(3sinβ/cosβ)^2sin^2α/cos^2α=9sin^2β/cos^2β=(9sin^2α）/4)/[(3+cos^2α）/4...