设集合A={x|kπ-π/4≤x≤kπ+π/4},B={x|x^2≤9},试求集合A交B

Question

设集合A={x|kπ-π/4≤x≤kπ+π/4},B={x|x^2≤9},试求集合A交B

Answer 1

B={-3≤x≤3}
k只能取-1、0、1
此时,A交B={-3≤x≤-3/4π或-1/4π≤x≤1/4π或3/4π≤x≤3}