TRIGONOMETRY FORMULAS = sec x cot 2 (x) +1 = csc x

TRIGONOMETRY FORMULAS

cos2 (x) + sin 2 (x) = 1

1 + tan 2 (x) = sec2 (x)

cot 2 (x) + 1 = csc2 (x)

cos(x ? y) = cos(x) cos( y) sin(x) sin( y) sin(x ? y) = sin(x) cos( y) ? cos(x) sin( y)

sin(2x) = 2sin(x) cos(x) cos2 (x) - sin 2 (x)

cos(2x) = 2 cos2 (x) -1 1 - 2sin 2 (x) 2 tan(x)

tan(2x) = 1 - tan 2 (x)

tan(x ? y) = tan(x) ? tan( y) 1 tan(x) tan( y)

c2 = a2 + b2 - 2ab cos(C)

sin( A) = sin(B) = sin(C)

a

b

c

sin 2 (x) = 1 - cos(2x) 2

cos2 (x) = 1 + cos(2x) 2

tan 2 (x) = 1 - cos(2x) 1 + cos(2x)

cos x = ? 1 + cos(x)

2

2

sin x = ? 1 - cos(x)

2

2

tan

x 2

=

?

1 - cos(x) 1 + cos(x)

sin(x)sin( y)

=

1 2

[cos(x

-

y)-

cos(x

+

y)]

cos(x) cos( y)

=

1 2

[cos(x

-

y)+

cos( x

+

y)]

sin(x) cos( y)

=

1 2

[sin(x

+

y)+

sin(x

-

y)]

cos(x) sin( y)

=

1 2

[sin(x

+

y)-

sin( x

-

y)]

sin(x) + sin( y) = 2sin x + y cos x - y 2 2

sin(

x)

-

sin(

y)

=

2

sin

x

- 2

y

cos

x

+ 2

y

cos(x)

+

cos(

y)

=

2

cos

x

+ 2

y

cos

x

- 2

y

cos(x)

-

cos(

y)

=

-2

sin

x

+ 2

y

sin

x

- 2

y

For two vectors A and B, A?B = ||A||||B||cos()

The well known results: soh, cah, toa

soh: s stands for sine, o stands for opposite and h stands for hypotenuse, sin x = o h

cah: c stands for cosine, a stands for adjacent h stands for hypotenuse, cos x = a h

o

h

toa: t stands for tan, o stands for opposite and a stands for adjacent, tan x = o

a

a

Where x is the angle between the hypotenuse and the adjacent.

Other three trigonometric functions have the following relations:

csc x =

1

= h , sec x =

1

h =

and

cot x =

1

a =

sin x o

cos x a

tan x o

Important values:

0 sin

0

cos 1

tan 0

csc undefined

sec 1

cot undefined

300 = 6

1 2 3 2 1 3

2 2 3

3

450 = 4

2 2 2 2 1

2

2 1

600 = 3

3 2 1 2

3 2 3

2 1 3

900 = 2

1 0 undefined 1 undefined 0

sin(n ? x) = [ ? ]sin x, cos(n ? x) = [ ? ]cos x, tan(n ? x) = [ ? ]tan x , the sign ? is for plus or minus

depending on the position of the terminal side. One may remember the four-quadrant rule: (All Students Take Calculus: A = all, S = sine, T = tan, C = cosine)

sine

all

tan

cosine

F2006 ? Department of Mathematics & Statistics ? Arizona State University

2

Example: Find the value of sin 3000 . We may write sin 3000 = sin(2 1800 - 600 ) = [-]sin 600 = - 3 , 2

in this case the terminal side is in quadrant four where sine is negative.

In the following diagram, each point on the unit circle is labeled first with its coordinates (exact values), then with the angle in degrees, then with the angle in radians. Points in the lower hemisphere have both positive and negative angles marked.

F2006 ? Department of Mathematics & Statistics ? Arizona State University

3

 ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download