cos20°cos10°-cos70°cos80°
2个回答
原式=cos20°cos10°-sin20°sin10°
=cos(20+10)°
=cos30°
=√3/2
相关问题
化简cos20/cos70-2cos10=
化简:(1)(cos²10°-cos²80°)²+cos²70°=? (2)(s
请证明(sin10)(cos10)(cos30)(cos50)(cos70)=(3/16)*(cos80),thx la
求值:(2sin80°-cos70°)/cos20°
﹙1/cos²80-3/cos²10﹚·1/cos20
(cos(70-20)-cos(70+20)为什么等于cos50?
计算题cos80°cos70°-sin80sin70
(sin50°(1+√3tan10°)-cos20°)/cos80°√(1-cos20°
cos20°•cos40°•cos60°•cos80°=( )
cos20°•cos40°•cos60°•cos80°=( )