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Measurement of Angles : Measurement of Angles Lesson 1 TRIGONOMETRY
Session Objective : Session Objective Measuring Angles
Relation between degree and radian www.aptacads.com
Measuring Angles : Measuring Angles Two systems of measuring angles
(i) Sexagesimal system (Degree)
The angle traced by a moving line about a point is 360°
1° = 60 minute =
= 60 second = www.aptacads.com
Slide 5 : (ii) Circular System (Radian)
A radian is an angle subtended by an arc at the centre of a circle whose length is equal to radius of the circle.
1 radian can be written as 1c
Relation between Degree and Radian : Relation between Degree and Radian
Example (1): Convert 60° into radian measuresince : Example (1): Convert 60° into radian measuresince Example (2): Convert 25° 20' into radian measure
Since
Slide 8 : Try it now Time : 6 min
Convert the following into radian measure
1. = _____ 4. = ____
2. = _____ 5. = ____
3. = _____
Slide 9 : Answer
4.
2. 5.
3.
Slide 10 : www.aptacads.com Example (3): Convert into degree measure.
Since
Slide 11 : Example 4: Convert 4 radian into degree measure
Since
Slide 12 : Try it now Time: 4 min
Convert the following into degree measure:
3.
4.
Slide 13 : www.aptacads.com Answer
= 150° 3. = 60°
= 270° 4. =
Slide 14 : www.aptacads.com Some Important conversions :
Let’s do it : Let’s do it Q 1. The angles of a triangle are in AP and the greatest angle is double the least. Find all the angles in degrees and radians.
Q 2. The difference between the two acute angles of a right triangle is . Find these angles in radians and degrees. www.aptacads.com
Slide 16 : Thanks www.aptacads.com