cos135°=？sin135°=？cos75°=？sin75°=？

两角和与差的三角函数公式 万能公式
sin（α＋β）＝sinαcosβ＋cosαsinβ
sin（α－β）＝sinαcosβ－cosαsinβ
cos（α＋β）＝cosαcosβ－sinαsinβ
cos（α－β）＝cosαcosβ＋sinαsinβ
然后套用公式
cos135°=cos(90°+45°)=cos90°cos45°－sin90°sin45°=-0.707
sin135°=0.707
cos75°=0.259
sin75°=0.966
或者用
sin（2π－α）＝－sinα =-sin45°=-0.707
cos（2π－α）＝cosα=cos45°=0.707

cos135
=-cos45
=-√2/2

sin135
=sin135
=√2/2

cos75
=cos(45+30)
=cos45cos30-sin45sin30
=(√2/2)(√3/2)-(√2/2)(1/2)
=(√6-√2)/4

sin75
=sin(45+30)
=sin45cos30+cos45sin30
=(√2/2)(1/2)+(√2/2)(√3/2)
=(√6+√2)/4

cos135
=-cos45
=-√2/2

sin135
=sin135
=√2/2

cos75
=cos(45+30)
=cos45cos30-sin45sin30
=(√2/2)(√3/2)-(√2/2)(1/2)
=(√6-√2)/4

sin75
=sin(45+30)
=sin45cos30+cos45sin30
=(√2/2)(1/2)+(√2/2)(√3/2)
=(√6+√2)/4
加分吧

Cos135°=cos(18