1980 年

In the figure, diameter $AB=2$. $\angle CAB=\dfrac{\pi}{10}$ rad. Minor arc $BC=$

In the figure, $\angle B=\angle C=90^\circ$. If $AB=p$ and $BC=q$, then $CD=$

In the figure, $AD$ and $BE$ bisect $\angle A$ and $\angle B$ respectively. $\angle C=$

In the figure, $O$ is the centre of the circle and its radius is $r$. $XY$ touches the circle at $P$. Find the distance of $Q$ from $XY$.

Which of the following is the graph of $y=2\sin\theta$, where $0\le\theta\le 2\pi$?

In the figure, $AB=BC=CD$. $\angle AED=$

In the figure, $RS$ is a tangent to the circle at $C$. $BA$ is any chord parallel to $RCS$. Which of the chords $AB$, $BC$ and $CA$ must be equal in length?

In the figure, $AOB$ is a diameter of the circle, centre $O$. $CD$ is the perpendicular bisector of $OA$. Which of the angles $a$, $b$, $c$, $d$ is/are equal to $30^\circ$?

In the figure, circle $O$ is inscribed in $\triangle ABC$, touching $BC$ at $X$. Which of the following must be true?

I. $OX\perp BC$ II. $OA$ bisects $\angle A$ III. $AO$ produced bisects $BC$

In the figure, $AC$ and $BC$ are diameters of two semi-circles touching each other internally at $C$. $PQC$ is a straight line. If $AB=1$, then $PQ=$