1/(2sin170°)-2sin70°
=(1-4sin70°sin170°)/2sin170°
=(1+2cos240°-2cos100°)/2sin170°
=-cos100°/sin170°
=sin10°/sin10°
=1
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1/(2sin170°)-2sin70°
=(1-4sin70°sin170°)/2sin170°
=(1+2cos240°-2cos100°)/2sin170°
=-cos100°/sin170°
=sin10°/sin10°
=1
如果本题有什么不明白可以追问,如果满意请点击“好评”