超簡單初中數學...............急!!!20分

1)slop(m)=?inclination(Θ)=102 度direction=?
slop(m)=-2.5inclination(Θ)=? direction=?
slop(m)=?inclination(Θ)=60度 direction=?
slop(m)=1inclination(Θ)=?direction=?

1. m= tan (102-180) = -4.7
direction NNW

-2.5 =tan angle
angle=-68.19
.'.Θ=111.8 degree
direction NNW

m= tan (60) = 1.7
direction NNE

Θ=45 degree
direction NE


2)show that L1//L2
L1(3,5)(8,0),L2 135度

mof L1 =-3/3=-1
m of L2 = -1
'.' m of L1=m of L2
.'. L1//L2

3)a(2,5)b(-2,3)c(4,1)are the three vertices of 3角形abc,show that 角a is a right angle
m of ab=2/4= 1/2
m of ac =4/-2 =-2
(m of ab)x(m of ac)=-1
.'. angle a is right angle

4)if the inclination of L1 is 60度and the slope of L2 is -1.5 findΘ
你個角係邊個角....

5)find the value of k
L1(2,3)(5,1),L2(6,k)(2,0)2線相交點90度
m of L1=2/-3
'.' they are right angle
.'. mof L1 x m of L2 =-1
.'. m of L2 =3/2
.'. k/(6-2)=3/2
k=6



2010-10-23 12:41:05 補充：
6)abcd is a square find the values of a
find the area of abcd
a(-2,3)b(2,9)c(8,5)d(a-1)

(3+1)/(-2-a)=(9-5)/(2-8)
6=2+a
a=4

area of abcd = [square root of (16+36) ]^2 =52 unit ^2

2010-10-23 12:45:14 補充：
7)ab//cd and M and N are mid-points of ac and bd respectively
find the coordinates of a
find the coordinates of M and N
Prove that MN//AB
a(0,a)b(8,0)c(6,12)d(8,11)MN 2點在梯形中間位


m of cd =1/-2= -0.5
'.' ab//cd
.'. m of ab = -0.5
a/-8=-0.5
.'.a=4

M (3,8)
N (8, 5.5)

2010-10-23 12:46:14 補充：
m of MN = 2.5/-5=-1/2
'.'m of MN=m of ab
.'. MN//AB