Where does radius sin angle sin rotation come from?

In summary, the formula for calculating a new "x" point of rotation involves applying the angle difference identity for cosine, resulting in x' = radius cos angle cos rotation - radius sin angle sin rotation. The minus sign may be a problem, but the wiki link provided by Jerry D. offers a solution.
  • #1
jerryd
2
0
For calculating a new "x" point of rotation I found the formula:

x' = radius * cos(angle + -rotation) which converts to:

x' = radius cos angle cos rotation - radius sin angle sin rotation

Where does "radius sin angle sin rotation" come from?

Jerry D.
 
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  • #2
jerryd said:
For calculating a new "x" point of rotation I found the formula:

x' = radius * cos(angle + -rotation) which converts to:

x' = radius cos angle cos rotation - radius sin angle sin rotation

Where does "radius sin angle sin rotation" come from?

Jerry D.

Hi jerryd! Welcome to MHB! ;)

It appears we're applying the angle difference identity for the cosine:
$$\cos(\alpha - \beta) = \cos\alpha \cos\beta + \sin\alpha \sin\beta$$
See for instance wiki.

However, we do seem to have a problem with a minus sign... (Worried)
 
  • #3
Thanks for the reply.

The link to Wiki answered everything.

Jerry D.
 

FAQ: Where does radius sin angle sin rotation come from?

What is the formula for calculating rotation?

The formula for calculating rotation is: θ = s/r Where θ represents the angle of rotation, s represents the arc length, and r represents the radius of the circle.

How does rotation formula differ from translation formula?

The rotation formula involves calculating angles and arc lengths, while translation formula involves calculating distances and displacements. Additionally, rotation involves a circular motion while translation involves a linear motion.

Can the rotation formula be used for 2D and 3D rotations?

Yes, the rotation formula can be used in both 2D and 3D rotations. In 2D rotations, the angle of rotation is measured in a single plane, while in 3D rotations, the angle of rotation is measured around a specific axis.

How is the direction of rotation determined using the formula?

The direction of rotation is determined by the positive or negative sign of the angle θ in the rotation formula. A positive angle indicates a counterclockwise rotation, while a negative angle indicates a clockwise rotation.

How is the rotation formula used in real-life applications?

The rotation formula is used in various fields, including engineering, computer graphics, and physics. It is used to calculate the rotation of objects, such as gears in a machine, the rotation of a planet around its axis, and the rotation of a 3D model in computer graphics.

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