Given that $O$ is the centre of the circle, prove that $2x-y=90°$.

Find the unknown angle $x$. 

Which of the following figures have both line and rotational symmetry?

Using $P$ as the centre of rotation, state the order of the rotational symmetry in this figure.

$RST$ is a tangent to the circle with centre $O$. $PS$ is a diameter. $Q$ is a point on the circumference and $PQT$ is a straight line. Angle $QST=37°$.

Write down the values of $a, b, c$ and $d$.

Write down the order of rotational symmetry of this shape.

Draw the lines of symmetry on this shape.

Write down the order of rotational symmetry of this shape.

$A, B$ and $C$ are points on the circumference of a circle centre $O$.

$OAD$ is a straight line and angle $DAB=142°$.

Calculate the size of angle of $ACB$.