Increasingly, Americans are becoming their own doctors by going to diagnose their symptoms, order home health tests or medical devices, or even self-treat their illnesses with drugs from Internet pharmacies(药店).Some avoid doctors because of the high cost of medical care, especially
Every day, more than six million Americans turn to the Internet
The problem is most people don’t know the safe way to surf the Web. “They use a search engine like Google, get 18 trillion choices and start clicking. But that’s risky, because almost anybody can put up a site that looks authoritative ( 权威的),so it’s hard to know if what you’re reading is

同类型试题

y = sin x, x∈R, y∈[–1,1],周期为2π,函数图像以 x = (π/2) + kπ 为对称轴
y = arcsin x, x∈[–1,1], y∈[–π/2,π/2]
sin x = 0 ←→ arcsin x = 0
sin x = 1/2 ←→ arcsin x = π/6
sin x = √2/2 ←→ arcsin x = π/4
sin x = 1 ←→ arcsin x = π/2


y = sin x, x∈R, y∈[–1,1],周期为2π,函数图像以 x = (π/2) + kπ 为对称轴
y = arcsin x, x∈[–1,1], y∈[–π/2,π/2]
sin x = 0 ←→ arcsin x = 0
sin x = 1/2 ←→ arcsin x = π/6
sin x = √2/2 ←→ arcsin x = π/4
sin x = 1 ←→ arcsin x = π/2

