Trig Identities Flashcards
1
Q
Cos(a-b)
A
Cos(a)Cos(b)+Sin(a)sin(b)
2
Q
Cos(a+b)
A
Cos(a)Cos(b)-Sin(a)sin(b)
3
Q
Sin(a-b)
A
Sin(a)Cos(b)-Cos(a)Sin(b)
4
Q
Sin(a+b)
A
Sin(a)Cos(b)-Cos(a)Sin(b)
5
Q
Tan(a+b)
A
1-tan(a)tan(b)
6
Q
tan(a-b)
A
1 + tan(a)tan(b)
7
Q
cos(2x)
A
cos(x+x)
cos(x)cos(x)-sin(x)sin(x)
cos^2 (x) - sin^2 (x)
2cos^2 (x) - 1
1-2sin^2 (x)
8
Q
sin(2x)
A
sin(x+x)
sin(x)cos(x)+cos(x)sin(x)
2cos(x)sin(x)
9
Q
tan(2x)
A
= tan(x+x)
2tan(x)
= —————–
1+ tan^2 (x)
10
Q
cos^2 (x)
A
2
11
Q
sin^2 (x)
A
2
12
Q
cos(x/2)
A
+- square root: 1+cos(x)/2
13
Q
sin(x/2)
A
+- square root: 1-cos(x)/2
14
Q
tan(x/2)
A
+- square root: 1-cos(x)/1+cos(x)
15
Q
A
