So, you seemed to have done well ! no e-mails ! I told you that you were brilliant ! Don't forget we're working for 24 100 percent and all getting over 75 percent in 2014 ! "Practice maketh Perfect !!!"
Today, we wish to do Ex 9 (B) : Nos 6, 5, 7, 8, 11
These sums involve reflection in lines other than the X-axis and Y-axis and in a point other than the Origin. However, our syllabus confines our study to lines parallel to the X-axis and the Y-axis.
You will remember that the equation of the X-axis is y=0 and the equation of the Y-axis is x = 0. Why is that so ? Because, the X-axis cuts the Y-axis at the point 0 and every point of the X-axis will have the ordinate 0; in the case of the Y-axis, it cuts the X-axis at 0 and on every point on the Y-axis the abscissa will be 0.
So, looking at page 121, example 5, you will see how to reflect a point in a line parallel to either the X-axis or the Y-axis. You need to remember the same rule : that the point which is reflected at the same distance from the line as its is reflection is from the line, however, the reflected point is on the other side of the line.
With that background - set off ! start off !
You might have to check the previous day's blog regarding types of triangles and quadrilaterals and their areas.
Have you come across the words perimeter ? It means the boundary - in triangles and quadrilaterals you add the lengths of the sides to find the perimeter. The formulae for some perimeters are :
Today, we wish to do Ex 9 (B) : Nos 6, 5, 7, 8, 11
These sums involve reflection in lines other than the X-axis and Y-axis and in a point other than the Origin. However, our syllabus confines our study to lines parallel to the X-axis and the Y-axis.
You will remember that the equation of the X-axis is y=0 and the equation of the Y-axis is x = 0. Why is that so ? Because, the X-axis cuts the Y-axis at the point 0 and every point of the X-axis will have the ordinate 0; in the case of the Y-axis, it cuts the X-axis at 0 and on every point on the Y-axis the abscissa will be 0.
So, looking at page 121, example 5, you will see how to reflect a point in a line parallel to either the X-axis or the Y-axis. You need to remember the same rule : that the point which is reflected at the same distance from the line as its is reflection is from the line, however, the reflected point is on the other side of the line.
With that background - set off ! start off !
You might have to check the previous day's blog regarding types of triangles and quadrilaterals and their areas.
Have you come across the words perimeter ? It means the boundary - in triangles and quadrilaterals you add the lengths of the sides to find the perimeter. The formulae for some perimeters are :
- P(square) = 4 x side
- P (rhombus) = 4 x side
- P(rectanangle) = 2 (length + breadth)
If you have any doubt - you know what to do !!!
Respected Brother,
ReplyDeleteCould you please help me with question no.11 of exercise 9(B) ,on page no.124.
Pravesh,
ReplyDeleteWhen point P is reflected in the X-axis it becomes P'(3,-4).
The line PP' is x=3, why ?
So, O' (reflected in the line PP' has the coordinates (6,0) - why ? O' will be the same distance from line PP' but on the opposite side of it, but on the X-axis
PP' is 8 units and OO' is 6 units - Do you understand why ? - because we are measuring the distance in PP' we take the ordinates because it is a vertical line and in OO' we take the abscissa because it is a horizontal line.
I hope that's clear - if it's not please ask again.
Bro.Miranda