cos135°=?sin135°=?cos75°=?sin75°=?

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°=cos(180°-45°)
=－cos45°(第二象限的角)
=－√2/2
Sin135°=sin(180°-45°)
=sin45°
= √2/2
cos75°=cos(45°+30°)
=cos45cos30-sin45sin30
=√2/2×√3/2-√2/2×1/2
=√6/4-√2/4
=(√6-√2)/4
Sin75=sin(45+30)
=sin45cos30+cos45sin30
=√2/2×√3/2+√2/2×1/2
=√6/4+√2/4
= (√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°=sin(90°-135°)=sin(-45°)=-sin45°sin135°=cos(90-135)°=cos(-45°)=cos45°
cos75°=cos(30°+45°)=cos30°*cos45°-sin30°*sin45°)
sin75°=sin(30°+45°)=sin30°*cos45°+sin45°*cos30°
结果自己算

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co...