is this possible with bi and tris?

When measuring bis flexed u actually are measuring both bi and tris right? So help me with this as I have never monitored this. When flexing for biceps peak only the bicep contract leaving triceps stretched with no peak and when flexing triceps only the triceps contract leaving the biceps stretched with no peak. So! Biceps flexed measures 45cm and triceps flexed measures 40cm. Now this is the part getting me into a spin, is it possible for the tricep measurement to go up say to 42cm without affecting the biceps peaked measurement?

It's difficult flexed because it'll never be accurate. The proper way to measure your arm is relaxed with your arm stretched out away from your body so you need someone else to do it.
Your measurements won't be as flattering but they'll be accurate so that you can track progress.

Ok so is it still possible then for the tri to get bigger without affecting the measurement of the flexed bi? The reason I'm asking is there's good progress with tris but the measurement on bis went up with just under a cm and neva came to think of it in this way