Trig Identities Flashcards
1
Q
sin(α - β)
A
sinα cosβ - cosα sinβ
2
Q
sin(α + β)
A
sinα cosβ + cosα sinβ
3
Q
cos(α - β)
A
cosα cosβ + sinα sinβ
4
Q
cos(α + β)
A
cosα cosβ - sinα sinβ
5
Q
tan(α - β)
A
(tanα - tanβ) / (1 + tanα tanβ)
6
Q
tan(α + β)
A
(tanα + tanβ) / (1 - tanα tanβ)
7
Q
sin^2θ+cos^2θ
Pythagorean trigonometric identity
A
1
Pythagorean trigonometric identity
8
Q
tan^2θ + 1
A
sec^2θ
9
Q
cot^2θ + 1
A
csc^2θ
10
Q
sin(2θ)
Double Angle Identity
A
2sinθcosθ
Double Angle Identity
11
Q
cos(2θ)
Double Angle Identity
A
cos^2θ - sin^2θ OR 1 - 2sin^2θ OR 2cos^2θ - 1
Double Angle Identity
12
Q
tan(2θ)
Double Angle Identity
A
(2tanθ) / (1-tan^2θ)
Double Angle Identity
13
Q
cosα cosβ
Product to Sum
A
1/2 [cos(α + β) + cos(α - β)]
Product to Sum
14
Q
cosx + cosy
Sum to Product
A
2cos((x + y) / 2) cos((x - y) / 2)
Sum to Product
15
Q
sin^2θ
Power Reducing Identity
A
[1 - cos(2θ)] / 2
Power Reducing Identity
