A circle is described by the equation x^2 + y^2 - 16x = 0. What is the length of the chord that is 4 units from the center of the circle?

A circle is described by the equation x2 + y2 - 16x = 0. What is the length of the chord that is 4 units from the center of the circle?

A. 12.563 units C. 8.523 units
B. 13.856 units D. 9.632 units

Given a right triangle where the hypotenuse is r, the acute angle theta, the opposite vertical side y and adjacent side x.

Given a right triangle where the hypotenuse is r, the acute angle θ, the opposite vertical side y and adjacent side x. Which of the following relations does not apply?

A. $1 + \tan^2 \theta = \sec^2 \theta$ C. $x^2 + y^2 = r^2$
B. $\cos 2\theta = 1 + 2\sin^2 \theta$ D. $\sin 2\theta = 2 (\sin \theta) (\cos \theta)$