Question

求下列函数的定义域①y=sinx+cosx.②y=(sinx+cosx)/tanx

Answer 1

(1)y=sinx,x∈ R

y=cosx,x∈ R

y=sinx+cosx,x∈R∩R=R

(2)y=(sinx+cosx),x∈R

y=1/tanx,x∈{x|x∈ R,x≠kπ/2}=Q

y=(sinx+cosx)/tanx,x∈R∩Q=Q={x|x∈ R,x≠kπ/2}