Cho hchóp S. ABC có đáy là tam giác vuông tại B, SA , O là trung điểm BC a) Chứng minh các mặt bên là các tam giác vuông?
b) Xác định góc giữa (SBC) và (ABC)
c) Tìm các khoảng cách d(A,(SBC) ; d(O,(SBC); d(AC, SB)

Use the quadratic formula to solve the equation. if necessary, round to the nearest hundredth. x^2 - 23 = 10x a. -1.93, 11.93 b. 1.93, -11.93 c. 1.93, 11.93 d. -1.93, -11.93

Geometry in the diagram, ∠abc is a right angle. ∠dbc = 30°27'40". find the measure of ∠abd.

Assume that there is a 11% rate of disk drive failure in a year. a. if all your computer data is stored on a hard disk drive with a copy stored on a second hard disk drive, what is the probability that during a year, you can avoid catastrophe with at least one working drive? b. if copies of all your computer data are stored on four independent hard disk drives, what is the probability that during a year, you can avoid catastrophe with at least one working drive?