(sina5π/12+cos5π/12)(sin5π/12-cos5π/12)
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（sin5π/12+cos5π/12)(sin5π/12-cos5π/12)=sin²5π/12-cos²5π/12
=(1-cos5π/6)/2-(1+cos5π/6)/2
=(1+√3/2)/2-(1-√ 3/2)/2
=√3/2
=(1-cos5π/6)/2-(1+cos5π/6)/2
=(1+√3/2)/2-(1-√ 3/2)/2
=√3/2
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(sin5π/12+cos5π/12)(sin5π/12-cos5π/12)
(sin5π/12+sinπ/12)(sin5π/12-sinπ/12)
=2sinπ/4cosπ/6 /2sinπ/6cosπ/4
=cotπ/6
=√3
(sin5π/12+sinπ/12)(sin5π/12-sinπ/12)
=2sinπ/4cosπ/6 /2sinπ/6cosπ/4
=cotπ/6
=√3
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[sin(5π/12)]^2 -[cos(5π/12)]^2=-cos(10π/12)=cos(π/6)=√3/2
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