Examination analysis: (1)① Draw a circle with point A as the center and point BC as the radius;

(2) Draw an arc with point A as the center and any length as the radius, intersecting with AB and AC edges at points E and F, then draw an arc with point B as the center and equal length as the radius, intersecting with AB at point M, and then draw an arc with point M as the center and EF length as the radius, intersecting with the previous arc at point N, and making ray BN to get ∠ Abd;

(2) AC∨BD can be obtained according to the fact that the internal angles are equal and the two straight lines are parallel, and then the distance from point A to BD is equal to the length of BC according to the equal distance between parallel lines, and then it is judged that the straight line BD is tangent to ⊙A according to the positional relationship between the straight line and the circle.

(1) as shown in the figure;

(2) The straight line BD is tangent to ⊙ a. 。

∫∠ABD =∠BAC，

∴AC∥BD，

∫∠ACB = 90°, and the radius ∫∫ A is equal to BC.

The distance from point A to straight line BD is equal to BC.

The straight line BD is tangent to a.

Comments: Drawing is the focus of junior high school mathematics, which runs through the whole junior high school mathematics study. It is a common knowledge point in senior high school entrance examination, which is generally not difficult and needs to be mastered skillfully.