In the plane rectangular coordinate system, if the ordinate of each point on the triangle is reduced by 3 and the abscissa remains the same, the obtained graph is based on the original graph ().

A. three units to the left.

B.it was translated down by 3 units.

C. translate up by 3 units.

D. translate 3 units to the right.

Answer b

In Rt△ABC, if the length of a right-angled side and hypotenuse is reduced to the original, the trigonometric function value of acute angle A is ().

A. Total contraction

B.nothing has changed

C. they are all expanded five times.

D. unable to determine

Answer b

It is known that in Rt△ABC, ∠ c = 90, tanA=, BC=8, then AC is equal to ().

A.6

B.

C. 10

D. 12

Answer a