TRIGONOMETRY
Sign for sin , cos and tan Quadrant I 0° < < 90° Quadrant II 90 ° < < 180° Quadrant III 180° < < 270° Quadrant IV 270 ° < < 360° ALL (+) SIN (+) TAN (+) COS (+) = Let = acute angle = 180 °− = 180 °+ = 360 °−
Finding angle when given sin Given that 0 ° 360°, find when sin = sin = − Quadrant II 90 ° < < 180° SIN (+) = 180 °− Quadrant III 180 ° < < 270° TAN (+) = 180 °+ Quadrant IV 270 ° < < 360° COS (+) = 360 °− sign (+) == sin = 50° (acute angle) = 50°, 130° Quad I & Quad II Quadrant I 0 ° < < 90° = sign ( − ) Quad III & Quad IV == sin = 35° = 180° + 35°, 360°−35° = 215°, 325°
Finding angle when given cos Given that 0 ° 360°, find when (a) (a) cos = (b) (b) cos = − Quadrant 2 90 ° < < 180° SIN (+) = 180 °− Quadrant ° < < 270° TAN (+) = 180 °+ Quadrant ° < < 360° COS (+) = 360 °− sign(+) == cos = 40° = 40°, 360 − 40° = 40°, 320° Quad I & Quad IV Quadrant I 0 ° < < 90° = sign ( − ) Quad II & Quad III == cos = 55° = 180° −55°, 180°+35° = 125°, 235°
Find angle when given tan Given that 0 ° 360°, find when (a) (a) tan = (b) (b) tan = −2.5 Quadrant 2 90 ° < < 180° SIN (+) = 180 °− Quadrant ° < < 270° TAN (+) = 180 °+ Quadrant ° < < 360° KOS (+) = 360 °− sign (+) == tan = 60°29’ Hence = 60°29’, 180° + 60°29’ = 60°29’, 240° 29’ Quadrant I and Quadrant 3 Quadrant 1 0 ° < < 90° = sign ( − ) Quadrant 2 and Quadrant 4 == tan = 68°12’ Hence = 180° − 68°12’, 360°−68°12’ = 111°48’, 291°48’
Practice makes perfect!!! 1. Given sin x° = and 90° x 180°, find x. 2. Given cos x = cos 34° and 270° x 360°, find x. 3. Given cos x = − and 90° x 180°, find x. 4. Given tan x = 0.8 and 180° x 360°, find x. 5. Given tan x = − and 270° x 360°, find x. Answer: (1) 131° (2)326° (3)133°50’ (4)218°40’ (5)321°