题目
cos负25π/12等于多少?
提问时间：2020-12-16
答案
cos(-25π/12)
= cos(25π/12)
= cos(2π+π/12)
= cos(π/12)
= cos{(π/6)/2}
= √{[1+cos(π/6)]/2}
= √{[1+√3/2]/2}
= √(2+√3)/2
= (√3+1)/(2√2)
= (√6+√2)/4
= cos(25π/12)
= cos(2π+π/12)
= cos(π/12)
= cos{(π/6)/2}
= √{[1+cos(π/6)]/2}
= √{[1+√3/2]/2}
= √(2+√3)/2
= (√3+1)/(2√2)
= (√6+√2)/4
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