Geometry Challenge

[Johnh]

Thanks Albert

Once id seen that nice round 85 degree result, I suspected there'd be an exact formula solution, and I thank you for showing it.

Those trig equivalencies are like old-school mathe-magic! Despite a lifetime of working things out, I haven't seen them directly in 45 years since high school.

Also, since this is a calc forum, I was quite impressed with the triangle solver on my HP39GII, once squinted at in order to read it. It can solve with any three of 3 sides and 3 angles, (so long as it gets at least one side)