I am creating a spreadsheet for solving "Solution of Triangles).
For the most part everything works well except for one situation.

In: B51 (Angle A)--------------J51 (Angle B)
So in J51 the formula is "=B51-90"
It works as long as there is data in B51. But when the cell is empty the
answer I get is 90 with the degree symbol because the cell is formated to
show the answer with the degree symbol.
How can this formula in J51 be modified to show an empty cell when B51 has
no input yet?

Many Thanks in advance.
Serge