sin12°cos18°-sin78°cos108°=?
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sin12°cos18°-sin78°cos108°=?sin12°cos18°-sin78°cos108°=?sin12°cos18°-sin78°cos108°=?sin12°cos18°-sin
sin12°cos18°-sin78°cos108°=?
sin12°cos18°-sin78°cos108°=?
sin12°cos18°-sin78°cos108°=?
sin12°cos18°-sin78°cos108°=sin12°cos18°-sin(90°-12°)cos(90°+18°)=sin12°cos18°+cos12°sin18°=sin(12°+18°)=sin30°=0.5
原式=sin12cos18-cos12(-cos72)
=sin12cos18+cos12sin18
=sun(12+18)
=sin30
=1/2
sin78°cos18°-sin12°sin162°=
sin12°cos18°-sin78°cos108°=?
解一个数学三角涵数题sin12°cos18°+sin78°cos72°
sin72°sin78°-sin18°sin12°=
sin12度*cos18度+sin78度*cos12度,
sin18°sin78°+sin72°sin12°=(要过程)
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(sin12°+cos30°sin18°)/(cos12°-sin30°sin18°)天哪,你家老师教你cos30=cos12+cos18?
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