=2sin20°+cos10°+
sin20°sin10° |
cos20° |
=
2sin20°cos20°+cos10°cos20°+sin20°cos10° |
cos20° |
=
sin40°+cos10° |
cos20° |
=
cos50°+cos10° |
cos20° |
=
2cos30°?cos20° |
cos20° |
=2cos30°
=
3 |
故答案為:
3 |
sin20°sin10° |
cos20° |
2sin20°cos20°+cos10°cos20°+sin20°cos10° |
cos20° |
sin40°+cos10° |
cos20° |
cos50°+cos10° |
cos20° |
2cos30°?cos20° |
cos20° |
3 |
3 |