题目
化简:
sin7°+cos15°sin8° |
cos7°−sin15°sin8° |
提问时间:2020-07-18
答案
因为cos15°sin8°=
[sin(8°+15°)+sin(8°-15°)=
(sin23°-sin7°)],
sin15°sin8°=
(cos7°-cos23°),
所以
=
=
=tan15°=tan(45°-30°)
=
=2-
1 |
2 |
1 |
2 |
sin15°sin8°=
1 |
2 |
所以
sin7°+cos15°sin8° |
cos7°−sin15°sin8° |
sin23°+sin7° |
cos23°+cos7° |
=
2sin15°cos8° |
2cos15°cos8° |
=
tan45°−tan30° |
1+tan45°tan30° |