求下列各角的正弦,余弦及正切函数值:(1)390度 (2)-7/4兀 (3)19/3兀

Question

如题所述

Answer 1

sin390=sin30=1/2
cos390=cos30=√3/2

tan390=sin390/cos390=√3/3
sin(-7π/4)=sin(π/4)=√2/2

cos(-7π/4)=cos(π/4)=√2/2

sin(19π/3)=sin(π/3)=√3/2

cos(19π/3)=cos(π/3)=1/2

Answer 2

a= 390° －7π/4 19π/3
sina 1/2 √2/2 √3/2
cosa √3/2 √2/2 1/2
tana √3/3 1 √3

Answer 3

写不下.

参考资料：解：(1)sin390°=sin(360°+30°)=sin30°=1/2;