1.Find the equation of the straight line which passes through (-1,2) and is perpendicular to the line x - y + =0.
2.A boy of 1m tall has a shadow of length 2m long. Find the angle of elevation of the sum correct to the nearest degree.
3.There are 12 balls in a box 8 of them are red and the others are yellow.Two balls are drawn at random, one after the other without replacement. Find the probability of getting two red balls.
煩請幫忙mat
2007-05-31 1:21 am
回答 (2)
2007-05-31 1:59 am
✔ 最佳答案
1)the slope of the line x-y+? =0 is 1so the slope of required line is -1
(y-2)/(x+1)= -1
y-2 = -x -1
x+y -1 =0
so the equation is x+y-1=0
2) Let x be the angle
tan x = 1/2
x= 27
so the angle is 27 degree
3) probability = 8/12x7/11
= 14/33
2007-05-31 2:07 am
For the first question ,what is the equation of the line which is perpendicular to the unknown equation and is there any missing information in x-y+?? =0 ?But I can still help you .
First , you have to find out the slope of x-y+ ? =0 by y=mx + c where m is the slope and c is a constant .So the m is 1 . Then find out the slope of required equation by
slope = -1/m (i.e. -1 ) .
Secondly , by using the equation (y-a)/(x-b)=slope where (a , b) is the given passing point. Therefore , the required equation is x+y-1=0 .
For the second question ,Let A be the angle of elevation .tanA=1/2, so A= 27'
For the thrid question , the required probabilty = 8/12 x 7/11 = 14/33 .
Hope these can help you .
First , you have to find out the slope of x-y+ ? =0 by y=mx + c where m is the slope and c is a constant .So the m is 1 . Then find out the slope of required equation by
slope = -1/m (i.e. -1 ) .
Secondly , by using the equation (y-a)/(x-b)=slope where (a , b) is the given passing point. Therefore , the required equation is x+y-1=0 .
For the second question ,Let A be the angle of elevation .tanA=1/2, so A= 27'
For the thrid question , the required probabilty = 8/12 x 7/11 = 14/33 .
Hope these can help you .
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