Grade 7 MATH | INTERIOR and EXTERIOR Angle of Polygon First Term (Term 1) Week 3 Revised K to 10

The video introduces the concepts of interior and exterior angles of a polygon. An exterior angle is formed when a side of a polygon is extended outward, and the sum of all exterior angles in any polygon is always 360 degrees. An adjacent interior angle is an angle inside the polygon that shares a common side with an exterior angle. The sum of an exterior angle and its adjacent interior angle is always 180 degrees.

Using a triangle, the video demonstrates how exterior and adjacent interior angles are formed when a side is extended. It labels different exterior (1, 4, 6) and interior (2, 3, 5) angles, explaining their adjacency and relationship.

The video uses a protractor to measure an exterior angle (150 degrees) and its adjacent interior angle (30 degrees) of a triangle. It shows that their sum is 180 degrees, confirming the definition of a linear pair.

Further examples with a triangle show how to find unknown exterior or interior angles given one of them, always maintaining the 180-degree sum. It also verifies that the sum of all exterior angles of the triangle (100, 110, 150 degrees) equals 360 degrees.

The video extends the discussion to a quadrilateral. It calculates unknown interior and exterior angles based on the 180-degree rule for adjacent pairs. It highlights that a square symbol indicates a 90-degree angle. The sum of interior angles in a quadrilateral is 360 degrees, and the sum of its exterior angles is also 360 degrees.

A pentagon is used as another example to demonstrate the relationships between interior and exterior angles. For each vertex, the sum of the interior and its adjacent exterior angle is 180 degrees. The total sum of exterior angles for the pentagon is confirmed to be 360 degrees, while the sum of its interior angles is 540 degrees.

The video concludes with an activity involving a quadrilateral where viewers are asked to determine unknown interior and exterior angles based on the principles discussed. It reiterates that the sum of exterior angles in any polygon is consistently 360 degrees, unlike interior angles which have a separate formula (to be covered in a future video). The answers to the activity are provided at the end of the video.