17×206= 18×470= 50×250=

五．动手操作。（共10分）

1．请用量角器画一个钝角，并标出它的度数。（2分）

2．过点A作已知直线的平行线和垂线。（4分）

3．在下面点子图上画一个平行四边形和一个梯形，再画出它们的高。（4分）

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