C4 vectors

You know the area

You know the length of AB so you know the perpendicular distance from AB to C

Reply 2

OP

Original post by TenOfThem

You know the area

You know the length of AB so you know the perpendicular distance from AB to C

How? Area is 16 ab is 15

Reply 3

Original post by printergirl

How? Area is 16 ab is 15

The area of a triangle is 1/2 base x perpendicular height

Reply 4

OP

Original post by TenOfThem

The area of a triangle is 1/2 base x perpendicular height

Isn't the area of whole triangle 16 , where c meets ab is perpendicular this splits the triangle?

Reply 5

Original post by printergirl

Isn't the area of whole triangle 16 , where c meets ab is perpendicular this splits the triangle?

Sorry, I do not understand your issue

The perpendicular height usually "splits" the triangle

Reply 6

OP

Original post by TenOfThem

Sorry, I do not understand your issue

The perpendicular height usually "splits" the triangle

So what do you do? Triangle ABC isn't right angled is it?

Reply 7

Original post by printergirl

So what do you do?

You use the facts that you have

•

you know the area

•

you know AB

•

you know that area=1/2 x base x perpendicular height

•

you want the perpendicular height

Reply 8

OP

Original post by TenOfThem

You use the facts that you have

•

you know the area

•

you know AB

•

you know that area=1/2 x base x perpendicular height

•

you want the perpendicular height

How you know ABC is right angled?

Reply 9

jarasta

12

Original post by printergirl

I have don parts a-e correctly and am stuck on f
I know that length BC=√93 but do not know what to do know. Do I use cosine rule? Or do I have to work out dot product? Please can you give a step by step guide

you could use area is equal to, absinc

i havent done the question, but from reading what they have asked. that sounds like a reasonable assumption. PS what book is that you are using?

Reply 10

Ayakashi

Original post by printergirl

How you know ABC is right angled?

cus c is perpendicular to AB - hence right angled, for perpendicularity must be 90 degrees (says so in part f)

Reply 11

OP

Original post by Ayakashi

cus c is perpendicular to AB - hence right angled, for perpendicularity must be 90 degrees (says so in part f)

O I c! I thought a line from c going towards a point on ab making it perpendicular!
why is this not the case?!

Reply 12

Ayakashi

Original post by printergirl

O -O I c! I thought a line from c going towards a point on ab making it perpendicula!
why is this not the case?!

the triangle is a point A, B and C, a line passes through A and B and C is perpendicular, connect the dots and u get a triangle! - Draw it out!

Reply 13

Original post by printergirl

How you know ABC is right angled?

Original post by printergirl

O I c! I thought a line from c going towards a point on ab making it perpendicular!
why is this not the case?!

Draw a triangle

AB is the base

C is the third vertex

Drop a perpendicular from C to the line AB (it meets the line at some point)

This line x AB x 1/2 = the area of the triangle

You know that this is how you find the area of a triangle ... you have probably know since you were 11

I am failing to see what you do not get

(edited 11 years ago)

Reply 14

OP

Original post by TenOfThem

Draw a triangle

AB is the base

C is the third vertex

Drop a perpendicular from C to the line AB (it meets the line at some point)

This line x AB x 1/2 = the area of the triangle

You know that this is how you find the area of a triangle ... you have probably know since you were 11

I am failing to see what you do not get

I c. I thought a perpenficular at point ab

Reply 15