angles, triangles and polygons Flashcards
x < 90
acute
90 < x < 180
obtuse
x=90
right
180 < x < 360
reflex
x + y = 90
complementary
x + y = 180
supplementary
a + b = 180
adjacent angles on a straight line
a + b + c + d + e = 360
angles at a point
a = c, b = d (X)
vertically opposite angles
a = b (Z)
alternate angles, – // –
c = b (F)
corresponding angles, –//–
b + d = 180 (C)
interior angles, –//–
equilateral triangle
3 equal sides and 3 equal angles
isosceles triangle
2 equal sides and 2 equal angles
scalene triangle
all sides of different lengths; all angles are different
180 in a triangle
angle sum of a triangle
exterior = sum of interior opposite angles
exterior angle of a triangle
parallelogram
- 2 pairs of equal and parallel opposite sides
- 2 pairs of equal opposite angles
- diagonals bisect each other
rectangle
- 2 pairs of equal and parallel opposite sides
- 4 right angles
- diagonals are equal in length and bisect each other
rhombus
- 4 equal sides
- opposite sides are parallel
- 2 pairs of equal opposite angles
- diagonals bisect each other at right angles
square
- 4 equal sides
- opposite sides are parallel
- 4 right angles
- diagonals are equal in length and bisect each other at right angles
kite
- 2 pairs of equal adjacent sides
- opposite angles are equal
- one diagonal bisects the other diagonal at right angles
- one diagonal bisects a pair of opposite angles
trapezium
- 1 pair of parallel sides
triangle
3 sided
quadrilateral
4 sided
pentagon
5 sided
hexagon
6 sided
heptagon
7 sided
octagon
8 sided
nonagon
9 sided
decagon
10 sided
180 (n-2)
sum of interior angles of an n-sided polygon
360
sum of exterior angles of any polygon
180 (n-2) / n
one interior angle of an n-sided polygon
