1
Q
sin(−θ)
A
−sin θ
2
Q
cos2A
A
cos2A–sin2A = 1–2sin2A = 2cos2A-1 = [(1-tan2A)/(1+tan2A)]
3
Q
sin x – sin y
A
2 cos [(x+y)/2] sin [(x-y)/2]
4
Q
cos(π/2-A)
A
sin A
5
Q
sin(2π-A)
A
-sin A
6
Q
sin(2π-A)
A
-sin A
7
Q
sin x + sin y
A
= 2 sin [(x+y)/2] cos [(x-y)/2]
8
Q
sin(π+A)
A
-sin A
9
Q
cot(A-B)
A
= [(cot A cot B + 1)/(cot B – cot A)]
10
Q
cos3A =
A
4cos3A – 3cosA
11
Q
sin3A =
A
3sinA – 4sin3A
12
Q
sin2A
A
2sinAcosA = [2tan A /(1+tan2A)]
13
Q
cos x – cos y
A
-2 sin [(x+y)/2] sin [(x-y)/2]
14
Q
tan 2A
A
(2 tan A)/(1-tan2A)
15
Q
cos(−θ)
A
cos θ
16
Q
cos(A+B)
A
cosAcosB - sinAsinB
17
Q
2cosAsinB
A
sin(A+B) - sin(A-B)
18
Q
tan(−θ)
A
−tan θ
19
Q
cot(A+B)
A
[(cot A cot B − 1)/(cot B + cot A)]
20
Q
sin(π/2-A)
A
cos A
21
Q
tan3A =
A
[3tanA–tan3A]/[1−3tan2A]
22
Q
cos(π-A)
A
-cos A
23
Q
cos(A-B)
A
cosAcosB + sinAsinB
24
Q
tan(A-B)
A
[(tan A – tan B)/(1 + tan A tan B)]
25
2sinAcosB
sin(A+B) + sin(A-B)
26
tan(A+B) =
[(tan A + tan B)/(1 – tan A tan B)]
27
cos(2π-A)
= cos A
28
sin(π-A)
sin A
29
-2sinAsinB
cos(A+B) - cos(A-B)
30
2sinAsinB
cos(A-B) - cos(A+B)
31
cos x + cos y
2 cos [(x+y)/2] cos [(x-y)/2]
32
cosec(−θ)
−cosecθ
XI
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