why is cos(-4x)=cos(4x)? teach me concepts. can add on to sin(-4x) tan(-4x)
Now, tan(x) is an odd function, since .
Does this clarify things?
If , then
hence, both angles have the same horizontal co-ordinate on the unit-circle.
Cos(angle)=horizontal co-ordinate of a point on the unit-circle circumference,
hence it can be located on the horizontal axis.
so the angles have the same horizontal co-ordinate.
Think of Cos(angle) as the horizontal co-ordinate of a point on the circle.
Sin(angle) is the vertical co-ordinate.
Tan(angle) is the slope of the line going through the origin (centre of unit-circle) and the point on the circle.
Or Tan(angle) is Sin(angle) divided by Cos(angle).
A positive angle is an anticlockwise movement starting at zero.
A negative angle is a clockwise movement starting at 360 degrees.