已知sin^2(30°)+sin^2(90°)+sin^2(150°)=1.5

来源：学生作业帮编辑：作业帮分类：数学作业时间：2024/05/06 05:39:26

已知sin^2(30°)+sin^2(90°)+sin^2(150°)=1.5
sin^2(5°)+sin^2(65°)+sin^2(125°)=1.5 观察两等式写出一般性命题并给出证明

sin^2(t-60)+sin^2(t)+sin^2(t+60)=1.5;
sin^2(t-60)+sin^2(t)+sin^2(t+60)
=(sintcos60-costsin60)^2+(sintcos60+costsin60)^2+sin^2(t)
=2(sintcos60)^2+2(costsin60)^2+sin^2(t)
=3/2((sint)^2+(cost)^2)
=3/2;

已知sin平方30度+sin平方90度+sin平方150度=3/2,sin平方5度+sin平方65度+sin平方125度计算：sin²1°+sin²2°+sin²3°...+sin²45°+sin&# 数列求和 sin²1°+sin²2°+sin²3°+.+sin²88°+sin& sin²1°+sin²2°+sin²89°+sin²88°= sin^2 (0°)+sin^2( 1°)+.+sin^2(90du) 求和已知tanα=2,计算:[sin(90°+α)-cos(180°-α)]/[sin(90°-α)-sin(180°-α) 已知2sin sin²1°+sin²2°+……sin²88°+sin²89° 已知sin(45°-α)=-2/3,45° 已知sin(45°-a)=-2/3,45° 为什么根号3sinα+cosα=2sin（α+30°）在Rt△ABC中,角C=90°,求证sin^2A+sin^2B=1,并利用上式求sin^21°+sin^22°+sin^