A. adj. Pertaining to the square of a square, or fourth power, of a number.
Biquadratic equation: an equation in which the unknown quantity is raised to the fourth power. Biquadratic parabola: a curve of the third order, having two infinite legs tending the same way. Biquadratic root: the square root of the square root (of a number).
1668. Pell, in Rigaud, Corr. Sci. Men, I. 132. The Latin paper concerning biquadratic equations.
1694. Phil. Trans., XVIII. 70. By extracting the Square Root, the Cubick, Biquadratick Roots, &c. of the Terms.
1804. Young, in Phil. Trans., XCV. 74. Determined by the solution of a biquadratic equation.
B. sb. a. The fourth power of a number. b. A biquadratic equation.
1661. Pell, in Rigaud, Corr. Sci. Men, I. 132. This biquadratic hath not four possible roots.
1727. Chambers, Cycl., Biquadratick, the next Power above the Cube.
1798. Wood, in Phil. Trans., LXXXVIII. 369. In cubics and biquadratics, the imaginary roots were found to be of this form, a+√–b2.
1838. Hallam, Hist. Lit., I. I. ix. § 5. The method of solving biquadratics.
