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  2. Proofs of trigonometric identities - Wikipedia

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

    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.

  3. Law of tangents - Wikipedia

    en.wikipedia.org/wiki/Law_of_tangents

    In trigonometry, the law of tangents or tangent rule [1] is a statement about the relationship between the tangents of two angles of a triangle and the lengths of the opposing sides. In Figure 1, a, b, and c are the lengths of the three sides of the triangle, and α, β, and γ are the angles opposite those three respective sides.

  4. Pitot theorem - Wikipedia

    en.wikipedia.org/wiki/Pitot_theorem

    A tangential quadrilateral is usually defined as a convex quadrilateral for which all four sides are tangent to the same inscribed circle. Pitot's theorem states that, for these quadrilaterals, the two sums of lengths of opposite sides are the same. Both sums of lengths equal the semiperimeter of the quadrilateral. [2]

  5. Pythagorean trigonometric identity - Wikipedia

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

    In this way, this trigonometric identity involving the tangent and the secant follows from the Pythagorean theorem. The angle opposite the leg of length 1 (this angle can be labeled φ = π/2 − θ) has cotangent equal to the length of the other leg, and cosecant equal to the length of the hypotenuse. In that way, this trigonometric identity ...

  6. Tangent lines to circles - Wikipedia

    en.wikipedia.org/wiki/Tangent_lines_to_circles

    By the power-of-a-point theorem, the product of lengths PM · PN for any ray PMN equals to the square of PT, the length of the tangent line segment (red). No tangent line can be drawn through a point within a circle, since any such line must be a secant line. However, two tangent lines can be drawn to a circle from a point P outside of the circle.

  7. Mollweide's formula - Wikipedia

    en.wikipedia.org/wiki/Mollweide's_formula

    In trigonometry, Mollweide's formula is a pair of relationships between sides and angles in a triangle. [1] [2]A variant in more geometrical style was first published by Isaac Newton in 1707 and then by Friedrich Wilhelm von Oppel [] in 1746.

  8. Dynamo star Hector Herrera sent off for spitting at ref ...

    www.aol.com/sports/dynamo-star-hector-herrera...

    Houston Dynamo star Hector Herrera was sent off with a straight-red card during the team's Sunday playoff match against the Seattle Sounders, about 30 minutes before the Dynamo's season ended with ...

  9. Descartes' theorem - Wikipedia

    en.wikipedia.org/wiki/Descartes'_theorem

    These are an infinite family of circles tangent to the -axis of the Cartesian coordinate system at its rational points. Each fraction / (in lowest terms) has a circle tangent to the line at the point (/,) with curvature . Three of these curvatures, together with the zero curvature of the axis, meet the conditions of Descartes' theorem whenever ...