what is corundum

what is Corundum Corundum mineral, crystalline-alumina (Al2O3), trigonal system, ditrigonal-skalenohedral. Occurs in the form of separate or fused into groups of barrel-shaped, dipyramidal and tabular crystals of pseudohexagonal appearance, isolated impregnations and ...

what does "identically equal" mean?

what does "identically equal" mean? either identically or equally. still say the identity is true To # 769; the (in mathematics) is an equality that is satisfied on the whole set of values ​​of the variables included in it (an equality that is true for any values ​​...