若P是等边三角形ABC所在平面外一点,PA=PB=PC=23,△ABC的边长为1,则PC和平面ABC所成的角是( ) A.30° B.45° C.60° D.90°
若P是等边三角形ABC所在平面外一点,PA=PB=PC=
,△ABC的边长为1,则PC和平面ABC所成的角是( )
A. 30°
B. 45°
C. 60°
D. 90°
2 |
3 |
A. 30°
B. 45°
C. 60°
D. 90°
数学人气:588 ℃时间:2019-08-19 12:01:46
优质解答
取AB中点D,连接PD、CD,∵PA=PB,D为AB中点,∴PD⊥AB,同理可得CD⊥AB∵PD、CD是平面PCD内的相交直线∴AB⊥平面PCD∵AB⊂平面ABC,∴平面PCD⊥平面ABC,由此可得直线PC在平面ABC内的射影是直线CD,∴∠PCD是直线PC...
我来回答
类似推荐
猜你喜欢
- 1forget about 英文定义填空:to try to_____________about someone or something that makes you unhappy.
- 2用科学的方法读书的诗句是什么
- 3白发老者可能对少年说了些什么呢?顶碗少年听了这后又会怎么想呢?试着想象一下,把
- 4You need to exercise more to keep fit .(同义句转化)
- 5我是中国人中表达了作者怎样的思想感情
- 6The paper was invented many c_______ ago by ancient Chinese.
- 7下列定义变量的语句中错误的是 .A)long _long; B)int _int_; C)char IF D)double us$;
- 8m和n是两个自然数,n=m+1,m和n的最大公因数是_,最小公倍数是_.
- 9they often have a time( ) (play)football after school what do you use your computer( ) (do)
- 10双曲线的离心率等于二分之根号五,与椭圆九分之X的平方加四分之Y的平方等于1有公共焦点,求此双曲线的方程