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# What is the definition of cos?

Top Answer

###### Wiki User

###### December 20, 2014 8:42PM

It's a variety of lettuce (Romaine lettuce).

## Related Questions

###### Asked in Definitions, Trigonometry

### Definition of 6 trigonometric functions?

sin(x) = x - x3/3! + x5/5! - x7/7! + ...
and
cos(x) = 1 - x2/2! + x4/4! - x6/6! + ... where x is the angle
measured in radians.
Then
tan(x) = sin(x)/cos(x) where cos(x) is not 0
cosec(x) = 1/sin(x) where sin(x) is not 0
sec(x) = 1/cos(x) where cos(x) is not 0
and
cot(x) = cos(x)/sin(x) where sin(x) is not 0

###### Asked in Math and Arithmetic

### What is cos 295?

###### Asked in Math and Arithmetic, Algebra

### How would you prove left cosA plus sinA right times left cos2A plus sin2A right equals cosA plus sin3A?

You need to make use of the formulae for sin(A+B) and cos(A+B),
and that cos is an even function:
sin(A+B) = cos A sin B + sin A cos B
cos(A+B) = cos A cos B - sin A sin B
cos even fn → cos(-x) = cos(x)
To prove: (cos A + sin A)(cos 2A + sin 2A) = cos A + sin 3A
The steps are to work with the left hand side, expand the
brackets, collect [useful] terms together, apply A+B formula above
(backwards) and apply even nature of cos function:
(cos A + sin A)(cos 2A + sin 2A) = cos A cos 2A + cos A sin 2A +
sin A cos 2A + sin A sin 2A
= (cos A cos 2A + sin A sin 2A) + (cos A sin 2A + sin A cos
2A)
= cos(A - 2A) + sin(A + 2A)
= cos(-A) + sin 3A
= cos A + sin 3A
which is the right hand side as required.