tan690°的值为( )
已知,则2a+3b的取值范围是()
等比数列前n项和为Sn,有人算得S1="8," S2="20," S3="36," S4=65,后来发现有一个数算错了,错误的是()
已知0<α<<β<π,又sin α=,cos(α+β)=-,则sin β=()
在中,若边长和内角满足,则角的值是()
已知数列为等差数列且,则的值为()