求值:cos 42° sin 72° - cos 48° sin18°=?
(4Sin30°Cos72°)/(Sin18°+Cos72°)+[Cos(45°+a)]/[Cos(45°-a)]-Co
求值:sin(10°+x)cos(50°-x)+sin(50°-x)cos(10°+x)
不查表求sin18°
三角函数的任意角问题化简求值,sin(-1320°)cos(-1110°)+cos(-1020°)sin750°+tan
求值:sin12°cos18°+cos12°sin18°=( )
急!已知cos(75°+θ)=1/3.θ为第三象限角求值:cos(-255°-θ)+sin(435°+θ)
求值sin^2A+cos^2(A+30°)+sinAcos(A+30°)
三角函数之求值问题sin²20°+cos²50°+sin20°cos50°=sin20°cos50
cos平方 48°+sin平方48°=
sinα+cosβ=sin225° sinα-cosβ=cos225°求cos(α-β)及cos(α+β)
化简 cos(a+b)cosa+sin(a+b)sina=_______ cos(31°-a)cos(29°+a)-co
计算不太明白...求值sin(-1320°)*cos1110°+cos(-1020°)sin750°+tan(-405°