Page 2 - Lesson Notes

 Acute-angled triangle:
o If all the three angles of a triangle are acute angles (i.e., each
measures less than 90°), it is called an acute-angled triangle.
Here, ∠XYZ, ∠YZX and ∠ZXY are all acute angles.

o Here, ∠XYZ, ∠YZX and ∠ZXY are all acute angles.
o XYZ is an acute-angled triangle.
 Right-angled triangle:
o If one of the angles of a triangle is a right angle (i.e., measures 90°),
it is called a right-angled triangle.

o Here, ∠XYZ = 90°. XYZ is a right angled triangle.
 Obtuse-angled triangle:
o If any one of the three angles of a triangle is an obtuse angles (i.e.,
measures more than 90°), it is called an obtuse-angled triangle.

o Here, ∠XYZ > 90°. XYZ is an obtuse-angled triangle.

Types of quadrilaterals : Quadrilateral is a polygon having 4 sides.

 Rectangle :

o A rectangle is a quadrilateral where every angle is a right angle (The
little squares in each corner mean "right angle") and
o opposite sides are parallel and of equal length.