trig identities to memorize

quotient identity for tan

sin/cos

quotient identity for cot

cos/sin

reciprocal identity for sin

1/csc

reciprocal identity for cos

1/sec

reciprocal identity for tan

1/cot

reciprocal identity for csc

1/sin

reciprocal identity for sec

1/cos

reciprocal identity for cot

1/tan

pythagorean identity for cos and sin

cos² + sin²=1

pythagorean identity for sec

tan²+1=sec²

pythagorean identity for csc

cot²+1=csc²

sum of angles for sin

sin a x cos b + cos a x sin b

sum of angles for cos

cos a x cos b - sin a x sin b

sum of angles for tan

(tan a + tan b)/ 1- tan a + tan b

difference of angles for sin

sin a x cos b - cos a x sin b

difference of angles for cos

cos a x cos b + sin a x sin b

difference of angles for tan

(tan a - tan b)/ 1 + tan a + tan b

double angle identity for sin

2 x sin x cos

double angle identity for cos with cos and sin

cos²-sin²

double angle identity for cos with sin

1-2 x sin²

double angle identity for cos with cos

2 x cos² - 1

double angle identity for tan

(2tan) / (1-tan²)

half angle identity for sin

+- square root of [ (1- cos) / 2 ]

half angle identity for cos

+- square root of [ (1+ cos) / 2 ]

half angle identity for tan

+- square root of [ (1- cos) / 1 + cos ]