tan θ = cosx ∈[-1 ,1]
θ ∈ [0 ,π/4] ∪ [3π/4 ,π]已知直線L；4X+3Y=c被兩坐標(biāo)軸截得線段長為1則c得值為？這題會做么？ 還有曲線3x^2-5x+1。在點(diǎn)1處的切線方程？x = 0 , y = c/3y = 0 , x = c/4√[(c/3)² + (c/4)²] = 1c = ±12/5f(x) = 3x² - 5x + 1f(1) = -1f'(x) = 6x - 5k = f'(1) = 1y - f(1) = k(x - 1)y + 1 = x - 1x - y - 2 = 0圓x^2+y^2-4x+6y-3=0上到x軸距離等于1的點(diǎn)有幾個？y = 1x² + 1 - 4x + 6 - 3 = 0x² - 4x + 4 = 0x = 2y = -1x² + 1 - 4x - 6 - 3 = 0x² - 4x + -8 = 0x = 2 ± 2√3共3個點(diǎn) (1 , 2) , (-1 , 2+2√3) , (-1 , 2-2√3)距離x為什么y等于1呢？距離x軸等于1的點(diǎn)的縱坐標(biāo)為1或-1均在y = 1 或 y = -1 上。