Introduction to Geometry
description
Transcript of Introduction to Geometry
Form 1 MathematicsChapter 6
SHW (III), Re-dictation & OBQ Today
SHW (I), Dictation, Re-dictation Correction
1 Feb (Fri) SHW (II), (III), Drawing, OBQ
Correction, Bring Textbook, Workbook 1B
4 Feb (Mon) CBQ
6 Feb (Wed)
Here are the answers: 1. 線段 Line Segment 2. 頂點 Vertex 3. 平行線 Parallel Lines 4. 垂直線 Perpendicular Lines 5. 鈍角 Obtuse Angle 6. 等腰三角形 Isosceles Triangle
Next we have: 7. 圓周 Circumference 8. 直徑 Diameter 9. 對角線 Diagonal 10. 正多邊形 Regular Polygon 11. 等邊五邊形 Equilateral
Pentagon 12. 等角六邊形 Equiangular
Hexagon
Correction: 10 times
Give the English name of the followings:
1. 銳角 2. 反角 3. 平面圖形 4. 曲面 5. 半徑 6. 相交
Give the English name of the followings:
7. 四邊形 8. 多面體 9. 等距畫圖 10. 均勻橫切面 11. 等邊三角形 12. 全等八角形
Can you get them all?
Here are the answers: 1. 銳角 Acute angle 2. 反角 Reflex angle 3. 平面圖形 Plane figure 4. 曲面 Curved surface 5. 半徑 Radius 6. 相交 Intersect
Next we have: 7. 四邊形 Quadrilateral 8. 多面體 Polyhedron / Polyhedra 9. 等距畫圖 Isometric drawing 10. 均勻橫切面 Uniform cross-section 11. 等邊三角形 Equilateral triangle 12. 全等八角形 Regular octagon
Can you get them all?
Points 點
Lines 線
Planes 面
Angles:
Name of angles (middle letter is vertex!)
There are six types:
When two lines in the same plane, but they do not intersect each other, they are called parallel lines ( 平行線 )
A pair of parallel lines is denoted by a pair of arrows ( 箭號 )
We write “AB // CD”
When two lines in the same plane are intersecting at right angle (90), they are called perpendicular lines ( 垂直線 )
A right angle willbe clearly shownin a pair of perpendicular lines
We write “AB CD”
Any shape enclosed by line segments in the same plane is called Plane Figure.
Otherwise, it should be a curved surface.
The name of the polygons depends on the number of straight lines:
Triangle 3 lines (Tri-) Quadrilateral 4 lines (Quadri-) Pentagon 5 lines (Penta-) Hexagon 6 lines (Hexa-) Octagon 8 lines (Octa-)
Number prefix (from wikipedia)
Diagonal ( 對角線 ) is the line segment joining any two non-adjacent ( 不相鄰 ) vertices ( 頂點 vertex)
A line segment joining two adjacent vertices is called a side ( 邊 )
Same side Equilateral ( 等邊 ) polygon Same angle Equiangular ( 等角 )
polygon Both Regular polygon ( 正多邊形 )
All points on the circle (circumference 圓周 ) are at the same distance (radius半徑 ) from the a fixed point (centre 圓心 ).
Diameter ( 直徑 ) is 2 x Radius (d = 2r)
C = d x ( 圓周率 )or C = 2r
3.14159 26535 897…
r
C
d
Triangles are formed by three straight lines
Its name depends on its angles
Sum of angles of a triangle is 180
a + b + c = 180 (Straight angle = 180)
Sum of : a + b + c = 180
Sum of : a + b + c = 180
Solids are 3-D (three-dimensional) figures.
PlaneVertex
Edge
Curved surface
Dotted lines
Isometric Drawing
1 cm 1 cm
1 cm
If we cut a solid at right angle to its length, the plane is called a cross-section.
If planes from the parallel cuts are the same, the plane is a uniform cross-section
When all faces of a solid are polygons only, it is called a polyhedron.
Yes! No!
The connected planes of a polyhedron are called a net.
Drawing Exercises & Dictation Today!!!!
SHW (III) & OBQ 30 Jan (Wed)
SHW (I), (II), Dictation Correction 1 Feb (Fri)
SHW (III), OBQ Correction 4 Feb (Mon)
CBQ 6 Feb (Wed)
Enjoy the world of Mathematics!
Ronald HUI