sin²20°+cos²50°+sin20°cos50°=__? 能告诉我过程吗?
来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/10/03 08:29:11
sin²20°+cos²50°+sin20°cos50°=__? 能告诉我过程吗?
sin²20°+cos²50°+sin20°cos50°
=(1-cos40°)/2+(1+cos100°)/2+(1/2)*(sin70°-sin30°)
=(1-cos40°)/2+(1-cos80°)/2+(1/2)*(cos20°-1/2)
=1-(1/2)*(cos40°+cos80°)+(1/2)*(cos20°-1/2)
=1-(cos60°cos20°)+(1/2)cos20°-1/4
=1-(1/2)cos20°+(1/2)cos20°-1/4
=3/4;
sin²20°+cos²50°+sin20°cos50°
=(sin20°+cos50°)^2-sin20°cos50°
=(sin20°+sin40°)^2-sin20°cos50°
=(2sin30cos10)^2-sin20°cos50°
=(cos10°)^2--[sin70-sin30]/2
=(1+cos20°)/2 -[cos20°-1/2]/2
=3/4;
=(1-cos40°)/2+(1+cos100°)/2+(1/2)*(sin70°-sin30°)
=(1-cos40°)/2+(1-cos80°)/2+(1/2)*(cos20°-1/2)
=1-(1/2)*(cos40°+cos80°)+(1/2)*(cos20°-1/2)
=1-(cos60°cos20°)+(1/2)cos20°-1/4
=1-(1/2)cos20°+(1/2)cos20°-1/4
=3/4;
sin²20°+cos²50°+sin20°cos50°
=(sin20°+cos50°)^2-sin20°cos50°
=(sin20°+sin40°)^2-sin20°cos50°
=(2sin30cos10)^2-sin20°cos50°
=(cos10°)^2--[sin70-sin30]/2
=(1+cos20°)/2 -[cos20°-1/2]/2
=3/4;
三角函数之求值问题sin²20°+cos²50°+sin20°cos50°=sin20°cos50
sin的平方20度+cos的平方50度+sin20度*cos50度=
1)求值sin^2 20度+cos^2 50度+sin20度cos50度
三角函数!计算:[sin20°*根号(1+cos40°)]/cos50°
2sin20°cos20°-2cos²25°
sin平方20°+cos平方80°+根号3sin20°cos80°
sin²20°+sin²80°-sin20°sin80°=?
根号(sin²70°)-根号(1-2sin20°×cos20°)+绝对值里(sin20°-1)
√(sin²70°)-√(1-2sin20°cos20°)+|sin20°-1|
求sin²20°+cos²80°+(根号3)sin20°cos80°的值
(√1+2sin20°cos20°)/(sin20°+√1-sin^2 20°)
化简sin20°分之sin^35°-1/2