c4 vectors

For part (e) working out the area of the triangle, why is my method of splitting the triangle into 2 and using Area =0.5absinC incorrect here? The answer should be 23.06

Is my diagram not accurate? my answers for a-d were correct.

thanks :smile:

@Zacken

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Reply 1

the bear

your method gives the correct area if the diagram is correct.

it looks like there is a right angle in the corner ?

Reply 2

Katiee224

Original post by the bear

your method gives the correct area if the diagram is correct.

it looks like there is a right angle in the corner ?

I don't think it's a right angle, just looks like it from my rough sketch :P

https://a086a5a2f39bda93734c56a63fab1d7be0a9ba38.googledrive.com/host/0B1ZiqBksUHNYQXE5T2xiNDBRd2s/January%202014%20(IAL)%20MA%20-%20C4%20Edexcel.pdf

in the model answers by arsey I have the same diagram but just used a different method, so not sure why I'm wrong :s-smilie:

Reply 3

the bear

Original post by Katiee224

is this yours or Arse's ? : https://a086a5a2f39bda93734c56a63fab1d7be0a9ba38.googledrive.com/host/0B1ZiqBksUHNYQXE5T2xiNDBRd2s/January%202014%20(IAL)%20MA%20-%20C4%20Edexcel.pdf

when i typed in your working i got 23.... maybe you were in radions or missed out a bracket ?

(edited 7 years ago)

Reply 4

Katiee224

Original post by the bear

They're the answers written by a member of this forum I believe,not mine

Reply 5

the bear

Original post by Katiee224

They're the answers written by a member of this forum I believe,not mine

anyway you were right... you must have typed it in wrong.

Reply 6

Katiee224

Original post by the bear

hmm maybe you're right, I'll try them again in my calculator :P

Reply 7

Katiee224

Original post by the bear

anyway you were right... you must have typed it in wrong.

I get the right ans when I type both angles as 77.2, but when I type in my working out I posted above, I get 23.06?

Reply 8

the bear

Original post by Katiee224

I get the right ans when I type both angles as 77.2, but when I type in my working out I posted above, I get 23.06?

so what is the correct answer ?

:holmes:

Reply 9

Katiee224

Original post by the bear

so what is the correct answer ?

:holmes:

did you get 23.4 when typing in my answer?

Reply 10

the bear

Original post by Katiee224

did you get 23.4 when typing in my answer?

23.06158337

Reply 11

Katiee224

Original post by the bear

23.06158337

aw right so my answers wrong, I think both angles arr 77.2 degrees but I'm not sure why :s-smilie:

Reply 12

the bear

Original post by Katiee224

aw right so my answers wrong, I think both angles arr 77.2 degrees but I'm not sure why :s-smilie:

it may be because both angles have been rounded before the working out ?

Reply 13

Katiee224

Original post by the bear

it may be because both angles have been rounded before the working out ?

nope that's not it, both angles should be 77.2 according to the mark scheme but I'm not sure why :s-smilie:

@Zacken any ideas?

Reply 14

Zacken

Original post by Katiee224

nope that's not it, both angles should be 77.2 according to the mark scheme but I'm not sure why :s-smilie:

@Zacken any ideas?

Where did you get 108.8 degrees from? It's a straight line, so both angles should add up to 180, yours ads up to 186. So the angle that's labelled 108.8 should be labelled 102.8.

Reply 15

Katiee224

Original post by Zacken

Where did you get 108.8 degrees from? It's a straight line, so both angles should add up to 180, yours ads up to 186. So the angle that's labelled 108.8 should be labelled 102.8.