1990 年

Which of the following graphs shows that $y$ is partly constant and partly varies inversely as $x$?

If $\sin\theta$ and $\cos\theta$ are the roots of the equation $x^2+k=0$, then $k=$

The figure shows the graph of $y=3\sin 2x$. The point $P$ is

In the figure, $ABCD$ is a parallelogram. $BD=$

In the figure, $A$, $B$ and $C$ are three points on the same horizontal plane. $A$ is due north of $B$, $C$ is due east of $B$ and $H$ is a point vertically above $A$. Which of the following angles is/are $90^\circ$? I. $\angle HAC$ II. $\angle ABC$ III. $\angle HBC$

In the figure, $AB$ is a diameter and $\angle BAC=30^\circ$. If the area of $\triangle ABC$ is $\sqrt{3}$, then the radius of the circle is

In the figure, $AC=CD$, $\angle ABC=30^\circ$ and $\angle CED=120^\circ$. $\dfrac{AB}{DE}=$

In the figure, $PA$ and $PC$ are tangents to the circle $ABC$. If $\angle P=48^\circ$, then $\angle ABC=$

In the figure, $EA$ and $EB$ are tangents to the circle $ABC$. If $EA\perp EB$ and $BD\perp AC$, find $\angle CBD$.

In the figure, if $CD=CF$, $CE=BE$ and $DA=DB$, then $\angle C=$