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Transcript
3 Unit Maths – Plane Geometry
5
Angle sum of triangle.
π‘Ž
𝑐
𝑏
π‘Ž
𝑏
∴ 𝒂 + 𝒃 + 𝒄 = πŸπŸ–πŸŽ°
Exterior angle of triangle.
𝑏
𝑐
π‘Ž
𝑑
π‘Ž + 𝑏 + 𝑐 = 180°
𝑐 + 𝑑 = 180°
𝑐 = 180° βˆ’ 𝑑
∴ π‘Ž + 𝑏 + 180 βˆ’ 𝑑 = 180
∴ 𝒂+𝒃= 𝒅
Angle sum of quadrilateral.
𝑏
𝑐
π‘Ž
𝑓
𝑑
𝑒
π‘Ž + 𝑏 + 𝑐 = 180° (1)
𝑑 + 𝑒 + 𝑓 = 180° (2)
(1) + (2)
∴ 𝒂 + 𝒃 + 𝒄 + 𝒅 + 𝒆 + 𝒇 = πŸ‘πŸ”πŸŽ°
Special lines in a triangle.
Angle bisector
An angle bisector is a line which bisects an angle.
Perpendicular bisector
A perpendicular bisector is a line which bisects the side and is also perpendicular to it.
Median
A median is the line drawn from a vertex to the midpoint of the opposite side.
Altitude
An altitude is a line from a vertex perpendicular to the opposite side.
Thompson Ly
1
3 Unit Maths – Plane Geometry
Sum of interior angles of nsided polygon.
Consider; the n-gon
𝐼𝑓 π‘’π‘Žπ‘β„Ž π‘£π‘’π‘Ÿπ‘‘π‘’π‘₯ 𝑖𝑠 π‘—π‘œπ‘–π‘›π‘’π‘‘ π‘‘π‘œ 0 π‘Žπ‘  π‘ β„Žπ‘œπ‘€π‘›, π‘‘β„Žπ‘’π‘› 𝑛 π‘‘π‘Ÿπ‘–π‘Žπ‘›π‘”π‘™π‘’π‘  𝑀𝑖𝑙𝑙 π‘“π‘œπ‘Ÿπ‘š, π‘’π‘Žπ‘β„Ž β„Žπ‘Žπ‘£π‘–π‘›π‘” π‘Ž π‘ π‘’π‘š π‘œπ‘“ 180°
∴ π‘‡β„Žπ‘’ π‘‘π‘œπ‘‘π‘Žπ‘™ π‘–π‘›π‘‘π‘’π‘–π‘Ÿπ‘–π‘œπ‘Ÿ π‘Žπ‘›π‘”π‘™π‘’ π‘ π‘’π‘š = 180°π‘›
π»π‘œπ‘€π‘’π‘£π‘’π‘Ÿ, π‘‘β„Žπ‘–π‘  π‘Ÿπ‘’π‘ π‘’π‘™π‘‘ 𝑖𝑛𝑐𝑙𝑒𝑑𝑒𝑠 π‘‘β„Žπ‘’ π‘Žπ‘›π‘”π‘™π‘’π‘  π‘Žπ‘‘ 0, π‘€β„Žπ‘œπ‘ π‘’ π‘ π‘’π‘š 𝑖𝑠 360°
∴ π‘Ίπ’–π’Ž 𝒐𝒇 π’Šπ’π’•π’†π’“π’Šπ’‚π’ π’‚π’π’ˆπ’π’†π’” 𝒐𝒇 𝒂𝒏 𝒏 βˆ’ π’ˆπ’π’ = πŸπŸ–πŸŽ°(𝒏 βˆ’ 𝟐)
Sum of exterior angles of nsided polygon.
Consider; the n-gon
π‘†π‘’π‘š π‘œπ‘“ π‘–π‘›π‘‘π‘’π‘Ÿπ‘–π‘œπ‘Ÿ π‘Žπ‘›π‘‘ 𝑒π‘₯π‘‘π‘’π‘Ÿπ‘–π‘œπ‘Ÿ π‘Žπ‘›π‘”π‘™π‘’ π‘Žπ‘‘ π‘’π‘Žπ‘β„Ž π‘£π‘’π‘Ÿπ‘‘π‘’π‘₯ = 180°
∴ π‘‡β„Žπ‘’ π‘‘π‘œπ‘‘π‘Žπ‘™ π‘–π‘›π‘‘π‘’π‘Ÿπ‘–π‘œπ‘Ÿ π‘Žπ‘›π‘‘ 𝑒π‘₯π‘‘π‘’π‘Ÿπ‘–π‘œπ‘Ÿ π‘Žπ‘›π‘”π‘™π‘’ π‘ π‘’π‘š = 180°π‘›
π»π‘œπ‘€π‘’π‘£π‘’π‘Ÿ, π‘‘β„Žπ‘’ π‘ π‘’π‘š π‘œπ‘“ π‘‘β„Žπ‘’ π‘–π‘›π‘‘π‘’π‘Ÿπ‘–π‘œπ‘Ÿ π‘Žπ‘›π‘”π‘™π‘’π‘  𝑖𝑠 180°(𝑛 βˆ’ 2).
∴ π‘Ίπ’–π’Ž 𝒐𝒇 π’†π’™π’•π’†π’“π’Šπ’π’“ π’‚π’π’ˆπ’π’†π’” 𝒐𝒇 𝒂𝒏 𝒏 βˆ’ π’ˆπ’π’ = πŸ‘πŸ”πŸŽ°
Question: Given the size of each angle in a polygon, find the number of sides.
ο‚· Use the exterior angle property.
Congruent tests
Side Side Side (SSS).
Side Angle Side (SAS).
Angle Angle Side (AAS).
Right angle Hypotunuse Side (RHS).
Properties to test for
quadrilaterals.
Parallelogram
ο‚· Opposite sides equal.
ο‚· Opposite sides parallel.
ο‚· Opposite angles equal.
ο‚· Pair of opposite sides are equal and parallel.
ο‚· Diagonals bisect each other.
Rhombus
ο‚· All sides are equal.
ο‚· Diagonals bisect at right angles.
Thompson Ly
2
3 Unit Maths – Plane Geometry
Rectangle
ο‚· All angles are right angles.
ο‚· Parallelogram with equal diagonals.
Square
ο‚· All sides equal and one angle is a right angle.
ο‚· All angles equal and two adjacent sides equal.
ο‚· Diagonals equal and bisect each other at right angles.
Intercept properties of a
transversal.
Properties
Similar tests.
Equiangular
All sides in same ratio
Two pairs of sides in same ratio and included angle equal.
Thompson Ly
3
3 Unit Maths – Plane Geometry
Pythagoras’ Theorem.
𝐴
𝑐
𝑏
β„Ž
𝐢
𝐡
π‘Ž
π»π‘’π‘Ÿπ‘’; βˆ†π΄π΅πΆ 𝑖𝑠 π‘ π‘–π‘šπ‘–π‘™π‘Žπ‘Ÿ π‘‘π‘œ βˆ†π΅πΆπ». βˆ†π΄π΅πΆ 𝑖𝑠 π‘ π‘–π‘šπ‘–π‘™π‘Žπ‘Ÿ π‘‘π‘œ βˆ†π΄πΆπ»
π‘Ž
𝐻𝐡
𝑏
𝐴𝐻
=
π‘Žπ‘›π‘‘ =
𝑐
π‘Ž
𝑐
𝑏
π‘Ž2 = 𝑐𝐻𝐡 π‘Žπ‘›π‘‘ 𝑏 2 = 𝑐𝐴𝐻
∴ π‘Ž2 + 𝑏 2 = 𝑐(𝐻𝐡 + 𝐴𝐻)
∴ π’‚πŸ + π’ƒπŸ = π’„πŸ
Areas
Triangle
𝑨=
𝟏
𝒃𝒉
𝟐
β„Ž
𝑏
Parallelogram
𝑨 = 𝒃𝒉
β„Ž
𝑏
Trapezium
𝒂+𝒃
𝑨 = 𝒉(
)
𝟐
π‘Ž
β„Ž
𝑏
Thompson Ly
4
3 Unit Maths – Plane Geometry
Rhombus
𝑨 = 𝒃𝒉
or
𝑨=
𝟏
𝟐
π’™π’š
𝑦
β„Ž
π‘₯
𝑏
Rectangle
𝑨 = 𝒃𝒉
β„Ž
𝑏
Square
𝑨 = π’™πŸ
π‘₯
Thompson Ly
5