Trig Identify Flashcards
1
Q
Pythagorean trig identities
A
sin^2(x) + cos^2(x) =1
sec^2(x) - tan^2(x) =1
csc^2(x) - cot^2(x) =1
2
Q
sin(-x)
A
-sinx
3
Q
cos(-x)
A
cosx
4
Q
tan(-x)
A
-tanx
5
Q
Law of cosine
A
(c^2) = (a^2) + (b^2) - (2ab)cos(c)
6
Q
Half angle: sin(x/2)
A
+/- √((1-cosx)/2)
7
Q
Half angle: cos(x/2)
A
+/- √((1+cosx)/2)
8
Q
Half angle: tan(x/2)
A
(1-cosx)/sinx
9
Q
sin2x
A
2sinxcosx
10
Q
cos2x
A
cos^2(x) - sin^2(x)
2cos^2(x) - 1
1 - 2sin^2(x)
11
Q
tan2x
A
2tanx / (1- tan^2(x))
12
Q
lim x->0 using sin/cos
A
((sinx + 1) / x ) = 1
((1 - cosx) / x ) = 0
13
Q
30° in radians
A
π/6
14
Q
60° in radians
A
π/3
15
Q
60° in radians
A
π/3
