## Thursday, 11 July 2013

### Lesson summary 11/7/2013

What we did today: (Content heavy stuff D:)

- Different angles of the unit circle and their coordinates

The unit circle is a circle with a radius of 1 and is on the coordinate system. The origin is at its centre, and when drawing a segment from the origin to any part of the circle, the coordinates of the intersection would be (cos θ, sin θ). (See earlier post on the chim lesson here for in depth explanation)

- Special angles / triangles

As seen in the middle of the board, certain angles and their trigonometric function answers can be found by drawing two different triangles, a triangle with 45º , 45º and 90º angles and an equilateral triangle that is perpendicularly bisected by a segment.

- How different angles in different quadrants relate to each other

On the right side of the board, the relationship between 20º, 160º, 200º and 340º is shown. sin 20º = sin 160º = -sin200º = -sin340º

By finding the angle between the segment from the origin to the circle circumference and the x axis, that angle can be added to added to 0º, subtracted from 180º, added to 180º and subtracted from 360º to find the set of special angles that relate to each other. (See the picture for more information)