- #1

mjxcrowley

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Hey everyone,

This has been bugging me for a bit. I think I'm probably missing something pretty easy.

There is the little shortcut that says where

What am I missing? How are both these things true?

Note: I don't want to mathematical derivation of the shortcut. I have that. I want to understand it in reality.

I hope this is in the correct forum

This has been bugging me for a bit. I think I'm probably missing something pretty easy.

**A**dot**B**= ABcos(θ), where θ is the angle between**A**and**B**.There is the little shortcut that says where

**B**is the derivative of**A**,**A**dot**B**= AB. Clearly then cos(θ) = 1, and the angle between a vector and its derivative is 2nPi, where n=0, 1, 2... Intuitively this would not be true, and is clearly not true for an orbit (which is what I use it for). There the angle between**R**and**V**where**V**is the derivative of**R**is 90°+the flight path angle.What am I missing? How are both these things true?

Note: I don't want to mathematical derivation of the shortcut. I have that. I want to understand it in reality.

I hope this is in the correct forum

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