Reproduced from http://teach.sg
$(90°)$
$(<90°)$
$(90° < θ < 180°)$
$(180° < θ < 360°)$
Angles on a straight line sum to $180°$
Angles around a point sum to $360°$
Vertically opposite angles are equal
Alternate Angles: Equal when lines are parallel
Corresponding Angles: Equal when lines are parallel
Interior Angles: Sum to $180°$ when lines are parallel
Angles on straight line = $180°$
Area = $\frac{a+b}{2} \times h$
Circumference = $2\pi r$
Area = $\pi r^2$
Surface Area = $2(lb + lh + bh)$
Volume = $l \times b \times h$
Surface Area = $2\pi r^2 + 2\pi r h$
Volume = $\pi r^2 h$
Volume = cross-sectional area × $l$
Volume = $\frac{1}{3} \times$ base area × height
Volume = $\frac{1}{3}\pi r^2 h$
Surface Area = $\pi r^2 + \pi r l$
Volume = $\frac{4}{3}\pi r^3$
Surface Area = $4\pi r^2$
A tangent to a circle is perpendicular to the radius at the point of contact.
The angle in a semicircle is always a right angle (90°).
Angles subtended by the same arc in the same segment are equal.
The angle at the centre is twice the angle at the circumference when subtended by the same arc.
Opposite angles in a cyclic quadrilateral sum to 180°.
Tangents drawn from an external point to a circle are equal in length.
Draw the line segment you want to bisect.
From each endpoint, draw arcs with the same radius (greater than half the line length).
Draw a line through the two intersection points. This is the perpendicular bisector.
Start with the angle you want to bisect.
From the vertex, draw an arc that intersects both arms of the angle.
From the intersection points, draw arcs with equal radius. Join the vertex to the intersection of these arcs.