Please i don't understand set theory in mathematics
1 answer:
Set theory is the mathematical theory of well-determined collections, called sets, of objects that are called members, or elements, of the set. ... The axioms of set theory imply the existence of a set-theoretic universe so rich that all mathematical objects can be construed as sets
For example, if A = {1, 2, 3} and B = {1, 2, 3, 4, 5} then A Í B (Í means is a subset of). If A = {1, 2, 4, 8}, then n(A) = 4. This is because n(A) means the number of members in set A. The universal set is the set of all sets.
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Consider right triangle ΔABC with legs AC and BC and hypotenuse AB. Draw the altitude CD.
1. Theorem: The length of each leg of a right triangle is the geometric mean of the length of the hypotenuse and the length of the segment of the hypotenuse adjacent to that leg.
According to this theorem,
Let BC=x cm, then AD=BC=x cm and BD=AB-AD=3-x cm. Then
Take positive value x. You get
2. According to the previous theorem,
Then
Answer:
This solution doesn't need CD=2 cm. Note that if AB=3cm and CD=2cm, then
This means that you cannot find solutions of this equation. Then CD≠2 cm.