You know A|B and A|C. Prove A|(B&C) by assuming A and separately by assuming B, then use case analysis (by dragging the first conclusion onto the second). To p

You know A|B and A|C. Prove A|(B&C) by assuming A and separately by assuming B, then use case analysis (by dragging the first conclusion onto the second). To prove A|(B&C) assuming B, you have to use A|C and yet another (nested) case analysis.