sin(45°+α)sin(45°-α)=1/6,α∈(90°,180°),求sin4α_数学解答

sin(45°+α)sin(45°-α)=1/6,α∈(90°,180°),求sin4α

人气：264 ℃　时间：2020-06-13 22:16:57

解答

sin(45°+α)sin(45°-α)=1/6∵sin(45°-α)=sin[90º-(45º+α)]=cos(45º+α)∴sin(45°+α)cos(45°+α)=1/6两边同时乘以22sin(45°+α)cos(45°+α)=1/3根据二倍角正弦公式：2sin(45°+α)cos(45°...