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A formula for computing the trigonometric identities for the one-third angle exists, but it requires finding the zeroes of the cubic equation 4x 3 − 3x + d = 0, where is the value of the cosine function at the one-third angle and d is the known value of the cosine function at the full angle.
Another method of deriving vector and tensor derivative identities is to replace all occurrences of a vector in an algebraic identity by the del operator, provided that no variable occurs both inside and outside the scope of an operator or both inside the scope of one operator in a term and outside the scope of another operator in the same term ...
The following are important identities in vector algebra.Identities that only involve the magnitude of a vector ‖ ‖ and the dot product (scalar product) of two vectors A·B, apply to vectors in any dimension, while identities that use the cross product (vector product) A×B only apply in three dimensions, since the cross product is only defined there.
The sign of the square root needs to be chosen properly—note that if 2 π is added to θ, the quantities inside the square roots are unchanged, but the left-hand-sides of the equations change sign. Therefore, the correct sign to use depends on the value of θ.
This article lists mathematical identities, that is, identically true relations holding in mathematics. Bézout's identity (despite its usual name, it is not, properly speaking, an identity) Binet-cauchy identity
The resulting identity is one of the most commonly used in mathematics. Among many uses, it gives a simple proof of the AM–GM inequality in two variables. The proof holds in any commutative ring. Conversely, if this identity holds in a ring R for all pairs of elements a and b, then R is commutative. To see this, apply the distributive law to ...
It follows that y 1 2 + y 2 2 + y 3 2 + y 4 2 = mr, for some strictly positive integer r less than m. Finally, another appeal to Euler's four-square identity shows that mpmr = z 1 2 + z 2 2 + z 3 2 + z 4 2. But the fact that each x i is congruent to its corresponding y i implies that all of the z i are divisible by m.
square-free integer A square-free integer is an integer that is not divisible by any square other than 1. square number A square number is an integer that is the square of an integer. For example, 4 and 9 are squares, but 10 is not a square. Szpiro Szpiro's conjecture is, in a modified form, equivalent to the abc conjecture.