## Manoj Chauhan is teaching live on Unacademy Plus

Trigonometry 1 Lecture INTRODUCTION The word 'Trigonometry' is derived from the Greek words 'trigon' and 'metron' and it means 'measuring the sides of a triangle'

Trigonometry b ADJACENT 1.ZA, 2. B and ZC are the three angles of triangle. a, b and c are BC, AC and AB respectively. the length of sides

Trigonometry ANGLES Terminal Side Vertex Initial side

Trigonometry SENSE OF AN ANGLE The sense of an angle is determined by the direction of rotation of the initial side into the terminal side. Vertex Initial side Vertex Initial side (i)Positive angle g 3.1 (ii) Negative angle

Trigonometry SOME USEFUL TERMS 1. QUADRANTS y-ars 10 10 10 (0,0) origin IV -10

Trigonometry 2. ANGLE IN STANDARD POSITION 90 45 180 36 360 all around) 270

Trigonometry 3. ANLGE IN QUADRANT .

Trigonometry 4. QUADRANT ANGLE Angles in the standard position where the terminal side lies on the x or y axis. For example: 90 , 180 etc.

Trigonometry 5. CO-TERMINAL ANGLES Coterminal angles: are angles in standard position (angles with the initial side on the positive x-axis) that have a common terminal side. For example, the angles 30 -330 and 390 are all coterminal (see figure 90 Terminal Side 180 30 39 0 Initial Side x 270

Trigonometry Example: Here 550, 415 , -305 are co-terminal 90" 305 415 55 Initial Side 180 0 Initial Side * 270