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  2. Proofs of trigonometric identities - Wikipedia

    en.wikipedia.org/wiki/Proofs_of_trigonometric...

    For example, the sine of angle θ is defined as being the length of the opposite side divided by the length of the hypotenuse. The six trigonometric functions are defined for every real number, except, for some of them, for angles that differ from 0 by a multiple of the right angle (90°). Referring to the diagram at the right, the six ...

  3. Proof that π is irrational - Wikipedia

    en.wikipedia.org/wiki/Proof_that_π_is_irrational

    This last integral is , since (+) is the null function (because is a polynomial function of degree ). Since each function f ( k ) {\displaystyle f^{(k)}} (with 0 ≤ k ≤ 2 n {\displaystyle 0\leq k\leq 2n} ) takes integer values at 0 {\displaystyle 0} and π {\displaystyle \pi } and since the same thing happens with the sine and the cosine ...

  4. Pythagorean trigonometric identity - Wikipedia

    en.wikipedia.org/wiki/Pythagorean_trigonometric...

    Point P(x,y) on the circle of unit radius at an obtuse angle θ > π/2 Sine function on unit circle (top) and its graph (bottom) The unit circle centered at the origin in the Euclidean plane is defined by the equation: [2] + =

  5. Elliptic curve - Wikipedia

    en.wikipedia.org/wiki/Elliptic_curve

    If x P = x Q, then there are two options: if y P = −y Q (case 3), including the case where y P = y Q = 0 (case 4), then the sum is defined as 0; thus, the inverse of each point on the curve is found by reflecting it across the x-axis. If y P = y Q ≠ 0, then Q = P and R = (x R, y R) = −(P + P) = −2P = −2Q (case 2 using P as R).

  6. Limit of a function - Wikipedia

    en.wikipedia.org/wiki/Limit_of_a_function

    For such a double limit to exist, this definition requires the value of f approaches L along every possible path approaching (p, q), excluding the two lines x = p and y = q. As a result, the multiple limit is a weaker notion than the ordinary limit: if the ordinary limit exists and equals L, then the multiple limit exists and also equals L. The ...

  7. Pythagorean theorem - Wikipedia

    en.wikipedia.org/wiki/Pythagorean_theorem

    So the three quantities, r, x and y are related by the Pythagorean equation, = +. Note that r is defined to be a positive number or zero but x and y can be negative as well as positive. Geometrically r is the distance of the z from zero or the origin O in the complex plane.

  8. Quartic function - Wikipedia

    en.wikipedia.org/wiki/Quartic_function

    The four roots of the depressed quartic x 4 + px 2 + qx + r = 0 may also be expressed as the x coordinates of the intersections of the two quadratic equations y 2 + py + qx + r = 0 and yx 2 = 0 i.e., using the substitution y = x 2 that two quadratics intersect in four points is an instance of Bézout's theorem.

  9. Square-integrable function - Wikipedia

    en.wikipedia.org/wiki/Square-integrable_function

    An equivalent definition is to say that the square of the function itself (rather than of its absolute value) is Lebesgue integrable.For this to be true, the integrals of the positive and negative portions of the real part must both be finite, as well as those for the imaginary part.