Block at rest on an inclined surface

[Akash47]

Sorry for that,I have edited my post.Now see it and clearly answer the questions.

 

[jbriggs444]

Sorry for that,I have edited my post.Now see it and clearly answer the questions.

Without having worked the problem your way, those formulas look plausible. But they go singular when $\mu$ = 1.

Hint: With $\mu$ = 1, the inclined plane could be vertical, the tangent would be infinite and the object would not fall. [Think of pressing a book against a wall to prevent its fall].

With $\mu$ > 1, is there still a limiting angle?

There is a different approach to the problem that removes the singularity. What if you started by combining W+F into one combined force and rotated your coordinate system by 45 degrees? [Don't forget that 45 degree offset when reporting your computed result]