ⓐ f(x)=0 ⓑ f(2π)=1
ⓒ f(−23π)=1 ⓓ x=−2π,−π,0,π,2π 일 때 f(x)=0
ⓔ (−2π,0), (−π,0), (0,0), (π,0), (2π,0) ⓕ (0,0)
ⓖ [−∞,∞] ⓗ [−1,1]
원본 교재 풀이(영어)
ⓐ f(x)=0 ⓑ f(2π)=1
ⓒ f(−23π)=1 ⓓ f(x)=0 for x=−2π,−π,0,π,2π
ⓔ (−2π,0), (−π,0), (0,0), (π,0), (2π,0) ⓕ (0,0)
ⓖ [−∞,∞] ⓗ [−1,1]