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HMMT 二月 1998 · ADV 赛 · 第 1 题

HMMT February 1998 — ADV Round — Problem 1

专题
Discrete Math / 离散数学
难度
L3
来源
HMMT

题目详情

  1. Evaluate sin( 1998 °+ 237 ° ) sin( 1998 °− 1653 ° ) . 2 2
解析
  1. Evaluate ◦ ◦ ◦ ◦ sin(1998 + 237 ) sin(1998 − 1653 ) . 1 ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ Answer: − . We have sin(1998 +237 ) sin(1998 − 1653 ) = sin(2235 ) sin(345 ) = sin(75 ) sin( − 15 ) = 4 ◦ sin(30 ) 1 ◦ ◦ ◦ ◦ − sin(75 ) sin(15 ) = − sin(15 ) cos(15 ) = − = − . 2 4