Тригонометрия.

sin x = a/c

cos x = b/c

tg x = a/b=sinx/cos x

ctg x = b/a = cos x/sin x

sin (p -a ) = sin a

sin (p /2 -a ) = cos a

cos (p /2 -a ) = sin a

cos (a + 2p k) = cos a

sin (a + 2p k) = sin a

tg (a + p k) = tg a

ctg (a + p k) = ctg a

sin² a + cos² a =1

ctg a = cosa / sina , a ¹ p n, nÎ Z

tga × ctga = 1, a ¹ (p n)/2, nÎ Z

1+tg² a = 1/cos² a , a ¹ p (2n+1)/2

1+ ctg² a =1/sin² a , a ¹ p n

Формулы сложения:

sin(x+y) = sin x cos y + cos x sin y

sin (x-y) = sin x cos y - cos x sin y

cos (x+y) = cos x cos y - sin x sin y

cos (x-y) = cos x cos y + sin x sin y

tg(x+y) = (tg x + tg y)/ (1-tg x tg y )

x, y, x + y ¹ p /2 + p n

tg(x-y) = (tg x - tg y)/ (1+tg x tg y)

x, y, x - y ¹ p /2 + p n

Формулы двойного аргумента.

sin 2a = 2sin a cos a

cos 2a = cos² a - sin² a = 2 cos² a - 1 =

= 1-2 sin² a

tg 2a = (2 tga )/ (1-tg² a )

1+ cos a = 2 cos² a /2

1-cosa = 2 sin² a /2

tga = (2 tg (a /2))/(1-tg² (a /2))