# Trig Identities and other Formulas

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1. Sin (a + b) =
Sin(a) Cos(b) + Sin(b) Cos(a)
2. Sin (a – b) =
Sin(a) Cos(b)- Sin(b) Cos(a)
3. Cos (a + b)=
Cos(a) Cos(b) – Sin(a) Sin(b)
4. Cos(a – b)
Cos(a) Cos(b) + Sin(a) Sin(b)
5. tan(a + b)
• tan(a) + tan(b)
• 1− tan(a) tan(b)
6. tan(a - b)
• tan(a) + tan(b)
• 1− tan(a) tan(b)
7. sin2x + cos2x =
1
8. 1 + tan2x =
sec2x
9. 1 + cot2x =
csc2x
10. sin 2u =
2sin(u) cos(u)
11. cos2u =
cos2u − sin2u
12. sin ( θ/2 )=
= ± squrt((1− cosθ)/2)
13. cos( θ/2 )=
= ± squrt((1− cosθ)/2)
14. tan ( θ/2 )=
• 1− cosθ
• sinθ

• sinθ
• 1 + cosθ
15. sinθ=
y/r
16. cosθ =
x/r
17. tanθ =
y/x
18. cscθ =
r/y
19. secθ =
r/x
20. cotθ =
x/y
21. 180o/π = π/180
1
22. sector =
α r
23. Area of a sector of a circle with angle α
A S= αr 2/ 2
24. Angular velocity
ω = α / time
25. Linear velocity
ν = s/t = αr/t = rω
 Author: hideeem ID: 115364 Card Set: Trig Identities and other Formulas Updated: 2011-11-08T05:36:05Z Folders: Description: Math 112 formulas Show Answers: