Yesterday was my mother's birthday.I gave her a g____.
There are only ________ new words in the book, but I know _______ of them.
下列说法不正确的是( )
如图,已知∠α和直角∠AOB,在∠AOB的内部以点O为顶点作∠β,使∠β=90°﹣∠α.(要求:尺规作图,不写作法,保留作图痕迹)