Combining gyro and accelerometer data

Hello people at the speartime i have beside studies im currently working on a quadcopter, but im kindoff stuck. I just cant seem to understand how to combine the angular rate from gyro and angle from accelerometer. Yes i know that commonly it is used kalman/complementary filter but i still cant seem to understand how its done(a mathematical explenation would be prefferd :slight_smile: )

Thanks for anny help!

This forum doesn't have any facility for writing mathematical equations, as far as I know. Another forum or a textbook would be better for this.

My usual problem is the explanations have too much maths.

Do not double post.