sin(-120°)cos(1290°)+cos(-1020°)sin(-1050°)=
sin(-1200°).cos1209°+cos(-1020°)-sin(-1050°)+tan855°
sinα+cosβ=sin225° sinα-cosβ=cos225°求cos(α-β)及cos(α+β)
(cos 45°-sin 30°)/(cos 45°+sin 30°)
Cos(180°+α)*sin(α+360°)/sin(-α-180°)*cos(-180°-α)
sin(x+105°)cos(x-15°)-cos(x+105°)sin求化简
cos平方 48°+sin平方48°=
sin²15°-cos²15°=
cos²15°-sin²15°=
Sin^2 45°+cos^2 45°=?
sin(a-360°)-cos(180°-a)=
cos ²15 °–sin²15 °= ----------.
-cos(α-45°)=sin(α+45°)对吗?