描點法畫函數(shù)y=238x+cos(51x+99)的性質及其圖像主要內(nèi)容：本文根據(jù)余弦等函數(shù)的有關性質，介紹通過描點法畫出三角函數(shù)y=238x+cos(51x+99)在區(qū)間[-EQ\F(4π+99,51),EQ\F(4π-99,51)]區(qū)間上圖像示意圖的主要過程與步驟。※.函數(shù)的定義域根據(jù)函數(shù)的特征，函數(shù)是一次函數(shù)y?=238x和余弦函數(shù)y?=cos(51x+99)的和函數(shù)，且二者的定義域為全體實數(shù)，所以其和函數(shù)的定義域也為全體實數(shù)，即為:(-∞，+∞)?！?函數(shù)描點思路由于函數(shù)y=238x+cos(51x+99)含有三角余弦函數(shù)，三角函數(shù)具有周期性值，故描點以三角函數(shù)為中心函數(shù)，分別取三角函數(shù)值為0，±1以及45°角時的取值為本例函數(shù)的特征點?！?函數(shù)的部分點圖本處以區(qū)間[-EQ\F(4π+99,51),EQ\F(4π-99,51)]為例，描點列為：x-2.188-2.172-2.157-2.141-2.12651x+99-4π-15π/4-7π/2-13π/4-3πcos(51x+99)10.710-0.71-1238x-520.74-516.94-513.37-509.56-505.99y-519.74-516.23-513.37-510.27-506.99x-2.111-2.095-2.080-2.064-2.04951x+99-11π/4-5π/2-9π/4-2π-7π/4cos(51x+99)-0.7100.7110.71238x-502.42-498.61-495.04-491.23-487.66y-503.1-498.6-494.3-490.2-487.0x-2.034-2.018-2.003-1.987-1.97251x+99-3π/2-5π/4-π-3π/4-π/2cos(51x+99)0-0.71-1-0.710238x-484.09-480.28-476.71-472.91-469.34y-484.1-481.0-477.7-473.6-469.3x-1.957-1.941-1.926-1.910-1.895-1.88051x+99-π/40π/4π/23π/4πcos(51x+99)0.7110.7100.71-1238x-465.77-461.96-458.39-454.58-451.01-447.44y-465.1-461.0-457.7-454.6-451.7-448.4x-1.864-1.849-1.833-1.818-1.803-1.78751x+995π/43π/27π/42π9π/45π/2cos(51x+99)-0.7100.7110.710238x-443.63-440.06-436.25-432.68-429.11-425.31y-444.3-440.1-435.5-431.7-428.4-425.3x-1.772-1.756-1.741-1.726-1.710-1.69551x+9911/4π3π13π/47π/215π/44πcos(51x+99)-0.71-1-0.7100.711238x-421.74-417.93-414.36-410.79-406.98-403.41y-422.4-418.9-415.1-410.8-406.3-402.4※.函數(shù)的示意圖y=238x+cos(51x+99) y (-1.695,-402.4)(-1.941,-461.0) x