1981 年

The radius of a sector is $3\text{ cm}$ and the perimeter is $10\text{ cm}$. What is the area of the sector?

The cone in Figure (b) is formed by bending the sector in Figure (a). The angle of the sector is $60^\circ$ and the radius is $12\text{ cm}$. The radius of the base of the cone is

In the figure, $\sin\theta=$

In the figure, $ABC$ is an equilateral triangle of side $2a$. $P$ and $Q$ are the mid-points of $AB$ and $AC$ respectively. $PQRS$ is a rectangle. What is the area of $PQRS$?

In the figure, $AB$ and $AC$ touch the circle at $B$ and $C$. If $P$ is any point on the minor arc $BC$, what is $\theta$?

In the figure, $AB\parallel CD\parallel EF$. $ACF$, $BCE$ and $BDF$ are straight lines. $AB=12$, $EF=6$. $CD=$ ?