my question is from klppner's text an introduction to mechanics, on page 26, they suppose a vector A(t) has a constant magnitude A, he states that the direction dA(t)/dt is always perpendicular to A(t), now they define [tex]\triangle A=A(t+\triangle t)-A(t)[/tex], he states that [tex]|\triangle A|=2Asin(\frac{\triangle\theta}{2})[/tex] i dont understand how did they arrive at the last equation, and dont understand which angle does he refer to. he states that it's defined in a sketch in the book but i cant find where does he state this?(adsbygoogle = window.adsbygoogle || []).push({});

thanks in advance.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: A question on vectors.

**Physics Forums | Science Articles, Homework Help, Discussion**