Page:Russell, Whitehead - Principia Mathematica, vol. I, 1910.djvu/151

SECTION A] $$\scriptstyle{\vdash:p.q.\supset.p\equiv q}$$

$$\scriptstyle{\vdash:p\supset q.\or.\sim p\supset q}$$

$$\scriptstyle{\vdash:p\supset q.\or.p\supset\sim q}$$

$$\scriptstyle{\vdash:p\supset q.\or.q\supset p}$$

$$\scriptstyle{\vdash:p\supset q.\or.q\supset r}$$

$$\scriptstyle{\vdash:p\equiv q.\or.p\equiv\sim q}$$

Dem.

$$\scriptstyle{\vdash.\sim(p\equiv q.p\equiv\sim q)}$$

Dem.

$$\scriptstyle{\vdash:p\or q.\sim(p.q).\equiv.p\equiv\sim q}$$

Dem.