C1 question Solomon I

It's Part C I'm having an issue with - for your info, the coords of Q and R are (15,0) and (0,15/4) respectively

I can't seem to get the required area, and don't understand why in the markscheme the triangles area is as simple as '1/2 * 15 * 15/4'

I know the area of a triangle is 1/2*b*h but I can't seem to understand the logic in the answer.

Thanks!

c1.png30.7KB

Scroll to see replies

Reply 1

Xzerzes

Because to find the area of the triangle on a graph x and y are base and height and so it is simply just 1/2*X*Y.
Question sounds a lot harder than it actually is tbf

Reply 2

iMacJack

Original post by Xzerzes

Because to find the area of the triangle on a graph x and y are base and height and so it is simply just 1/2*X*Y.
Question sounds a lot harder than it actually is tbf

I still don't get it.. because I thought you could only do this if the base and height are perpendicular

Reply 3

iMacJack

@Zacken accidently posted in A levels just realised sorry could you please move it (& also help pls :wink:

)

Reply 4

Zacken

Original post by iMacJack

@Zacken accidently posted in A levels just realised sorry could you please move it (& also help pls :wink:

)

Draw a sketch and post it up if it's still not screaming out at you. Remember that the axes are perpendicular to one another so it's a right-angled triangle.

Reply 5

Kevin De Bruyne

Original post by iMacJack

Draw a graph with those points and you will see that it is a right angled triangle (i.e half a square).

Reply 6

Xzerzes

X and Y are perpendicular though.
It is a right angle triangle with (0,0) (0,15/4) (15,0)
X2-X1= 15-0 = Base
Y2-Y1= 15/4-0 = Height

Reply 7

iMacJack

Original post by Zacken

Draw a sketch and post it up if it's still not screaming out at you. Remember that the axes are perpendicular to one another so it's a right-angled triangle.

ImageUploadedByStudent Room1463424009.598573.jpg

Rough sketch but it really isn't screaming out at me

Posted from TSR Mobile

Reply 8

techfan42

It's simple

Original post by iMacJack

Really simple, (1/2) x (15) x (15/4) = 225/8 = 28 1/8

Reply 9

techfan42

Original post by iMacJack

Rough sketch but it really isn't screaming out at me

Posted from TSR Mobile

OQR not PQR

Reply 10

iMacJack

Original post by techfan42

It's simple

Really simple, (1/2) x (15) x (15/4) = 225/8 = 28 1/8

Well, yes I am aware of that. It's the actual logic behind it I am not understanding - I appreciate the input however

Posted from TSR Mobile

Reply 11

iMacJack

Original post by techfan42

OQR not PQR

For.God.Sake I am an idiot oh lord lmao I SWEAR IT SAID PQR

Posted from TSR Mobile

Reply 12

Zacken

Original post by iMacJack

Rough sketch but it really isn't screaming out at me

Posted from TSR Mobile

Read the question, it says the triangle OQR. What is O? Its the origin.

Reply 13

techfan42

Original post by iMacJack

Well, yes I am aware of that. It's the actual logic behind it I am not understanding - I appreciate the input however

Posted from TSR Mobile

You did PQR, question says OQR where O is (0,0)

Reply 14

iMacJack

Well I am rather embarrassed at my lack of ability to read the question xD....

I honestly thought it was the triangle PQR, in which case I was like what wtf why have they just done 1/2 * b * h.. oh lord

Reply 15

techfan42

Original post by iMacJack

For.God.Sake I am an idiot oh lord lmao I SWEAR IT SAID PQR

Posted from TSR Mobile

hahahaha it's fine, I always misread the question

Reply 16

iMacJack

Thanks every one! That was a bit of a ridiculous error on my behalf.. well that serves me right I guess!!

Just to clarify - if it was PQR, you'd get the distances with the distance formula etc wouldnt you