sin^2 20°+cos^2 50°+sin30°sin70°

sin^2(20)-sin^2(25)sin(20)+cos^2(50)+cos^2(25)sin20 sin(10°)+sin(20°)cos(50°)求值 sin^2 30°+cos()=1 sin^2(20)+cos^2(50)+sin20sin50 3-cos 20°/2-sin ^2 80°等于 (cos^2 10°-cos^2 80°)+sin^2 20° 求值:3/(sin^2 20°)-1/(cos^2 20°)+64sin^2 20° sin^2(20°)+cos^(50°)+sin(20°)cos(50°)=?,不要用三个三角函数公式sina+sinb=2sin((a+b)/2)cos((a-b)/2 (cosa)^2 =1/2+1/2*cos2acos(a)cos(b)=1/2*[cos(a+b)+cos(a-b)]这个不能用 利用和差角公式化简 (2)sin(π/3+α)+sin(π/3-α)(2)sin(π/3+α)+sin(π/3-α)(3)cos(π/4+α)-cos(π/4-α)(4)cos(60°+α)+cos(60°-α)(5)sin(α-β)cosβ+cos(α-β)sinβ(6)cos(α+β)cosβ+sin(α+β)sinβ 化简 （1+sin a+ cos a)(sin a/2 - cos a/2) / √(2+2cos a)(180° sin^(2)20°+cos^(2)50°+sin20°cos50° sin^2 20°+cos^2 50°+sin30°sin70° 高中三角函数求值sin^2(20°)+cos^2(50°)+sin20°cos50°=? 2sin@+cos@等于? (cos^2)15°+(sin^2)15°等于多少 sin^2 80°为什么等于 cos^2 10°? Sin^2 45°+cos^2 45°=? 计算cos^2*105°-sin^2*105°