Angled Mitre Joints

[AlGBarker]

Hi guys,

I'm trying to build an intergrated corner bench in my decking. Cutting the joins in the seats is an easy job making 45 degree angles as they are horizontal. The back rests for the benchs however are a bit more tricky.

If the back rests were vertical, again it would just be a case of again cutting 45 degrees. However I don't want to build posture correction benchs and so want to build both back rests at an angle of 10 degrees from vertical.

I have a compound mitre saw, but as I've dicovered it isn't just a simple case of rotating the blade to 10 degrees and pitching it to 45 degrees.

Can anyone tell me how to calculate the angles??

Thanks,

Alan