合差化积:
1)
(54°+22°)/2=38°
sin54°+sin22°
=sin(38°+15°)+sin(38°-15°)
=(sin38°cos15°+cos38°sin15°)+(sin38°cos15°-cos38°sin15°)
=2 sin38°cos15°
2)
4°+52°)/2=28°
cos4°+cos52°
=cos(28°-24°)+cos(28°+24°)
=(cos28°cos24°+sincos28°sin24°)+(cos28°cos24°-sincos28°sin24°)
=2 cos28°cos24°
这个要用到积化和差公式,套公式应该可以做吧~
(1)= 2sin38 cos 32
(2)= 2cos28 cos 24