一个基因型为YyRr的精原细胞和一个同样基因型的卵原细胞,按自由组合定律遗传,各能产生几种类型的精子和卵细胞
A:2种和1种
B:4种和4种
C:4种和1种
D:2种和2种
—Before he went on the stage,he took a deep ______ .
—He was too nervous.
已知sinα=35,α∈(0,π2).sinβ=45,β是第二象限角.
(1)cos(α﹣β);
(2)tan2α;
(3)sin(π4+β)的值.