cos61°
=cos（60°+1°）
=cos60°*cos1°-sin60°*sin1°
cos60°=1/2=0.5
cos1°~1
sin60°=√3/2=0.866
sin1°~1°/180°π=0.0174
cos61°≈0.5*1-0.866*0.0174
≈0.485
近似计算cos61°的值 求详细的过程步骤
cos61°
=cos（60°+1°）
=cos60°*cos1°-sin60°*sin1°
cos60°=1/2=0.5
cos1°~1
sin60°=√3/2=0.866
sin1°~1°/180°π=0.0174
cos61°≈0.5*1-0.866*0.0174
≈0.485