求2sin20+cos10+tan20sin10的值,结果不要近似值,
问题描述:
求2sin20+cos10+tan20sin10的值,结果不要近似值,
答
2sin20+cos10+tan20sin10
=2sin20+cos20cos10/cos20+sin20sin10/cos20
=2sin20+cos(20-10)/cos20
=2sin20cos20/cos20+cos10/cos20
=(sin40+cos10)/cos20
=(cos50+cos10)/cos20
=2cos30cos20/cos20
=√3