题目

Indoor Plants As with any house guests, indoor plants require a certain amount of basic, regular attention if they are going to feel at home. The first consideration when purchasing plants is to make reasonably sure that they are suitable for the condition in which they are going to be housed. A general rule for most plans being brought indoors for the first time is to ensure that they have reasonable temperature of not less than 60 degrees Fahrenheit, a position out of cold air, safe from pets and not exposed to strong sunlight. Plants love company.When plants are growing together, th已知△ABC与△DBC都是边长为233的等边三角形，且平面ABC⊥平面DBC，过点A作PA⊥平面ABC，且AP=2．（Ⅰ）求直线PD与平面ABC所成角的大小；（Ⅱ）平面PDC与底面ABC所成的二面角的余弦值．