Geometric Reasoning Mahobe
The facts to learn
Angles in a triangle add up to 180o
Angles on a straight line add up to 180o
Angles around a point add up to 360o
base ∠’s isos ∆ =
∠ sum quad Interior angles of a quadrilateral sum to 360o
opp ∠, cyclic quad Opposite angles of a cyclic quadrilateral sum to 180o
Ext ∠, of cyclic quad Exterior angle of a cyclic quad equals the opposite interior angle
vert opp ∠s = Vertically opposite angles are equal
alt ∠s // lines Alternate angles are equal if the lines are parallel
corr ∠s // lines Corresponding angles are equal if the lines are parallel
Co-int ∠s // lines Co-interior angles sum to 180o if the lines are parallel
Exterior angles of a polygon add up to 360o
If the polygon is regular all exterior angles are the same size Exterior angles of a polygon add up to 360o
ext ∠ regular pentagon Exterior angles of a regular pentagon is 72o
Interior angles of a polygon with n sides sum to 180(n-2)
Find all the other angles in this figure
Vert opp angles
A triangle formed with 2 radii is isosceles
The angle at the centre is twice the angle at the circumference.
When writing angles use 3 letters When writing angles use 3 letters. The middle letter is where the angle is.
Find the angles u, v and w O Is the centre
O Is the centre
O Is the centre
O Is the centre
Find angle d
Calculate the size of angle ABC
Calculate angle CDE
Calculate the size of angle HIJ
Calculate the size of angle c
C = 96o, Co-int angle // lines Corr angles // lines OR Angles on a line Opp angles parallelogram
Calculate the size of angle VUW
Shape P is a regular pentagon and shape H is a regular heptagon Shape P is a regular pentagon and shape H is a regular heptagon. Calculate the size of angle CBD
Shape P is a regular pentagon and shape H is a regular heptagon Shape P is a regular pentagon and shape H is a regular heptagon. Calculate the size of angle CBD
The diagram gives the angles of a playground slide. Find angle XYZ.
Find the size of angles NMO and OPN
Find the size of angles NMO and OPN
Find the size of angles PRQ and PSQ
O
XBC 90 Rad perp. tang CBA 20 Angles on a line CAB Base angles isos triangle XCB 40 Ext angle = sum opp int angles CXB 50 Angle sum triangle
O Is the centre of the circle. Calculate the size of angle BCD
O Is the centre of the circle. Calculate the size of angle WYX
Similar triangles
ABC is an isosceles triangle. O is the centre of the circle ABC is an isosceles triangle. O is the centre of the circle. Calculate the size of angles BAC and ODC
Calculate the size of angles x and y.
.
O is the centre of the circle. Calculate the size of angle BAC.
.
KNML is cyclic as the opposite angles sum to 180.
O is the centre of the circle. Prove angle CBY = angle CAB
angle CBY = angle CAB