Is my answer correct?

The graph is below but my answer is

Yes, Lines A and B are perpendicular this is because they both intercept causing a right angle and they are opposite reciprocals of each other

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Did you calculate the gradient of each line?

(edited 3 years ago)

Reply 3

davros

Original post by Kakakaty

The graph is below but my answer is

Yes, Lines A and B are perpendicular this is because they both intercept causing a right angle and they are opposite reciprocals of each other

I haven't checked, but if you are sure that the lines are perpendicular then you need to say something about their gradients.

Reply 4

username5118974

Original post by medicalsupernova

Did you calculate the gradient of each line?

Oh no I didnt, I just did and I get different answers does that mean they're not?

Anyone know?

Original post by Kakakaty

Oh no I didnt, I just did and I get different answers does that mean they're not?

What are your values for the gradients of each line?

What do you know about the gradients of perpendicular lines?

Reply 7

username5118974

Original post by davros

What are your values for the gradients of each line?

What do you know about the gradients of perpendicular lines?

for A i got 3 and for B i got 2.5
I know that their gradients will multiply together to give -1 but from the gradient I got they don't equal -1 so does that mean theyre not perpendicular or did i do my calculations wrong?

Reply 8

mnot

Universities Forum Helper

Original post by Kakakaty

Oh no I didnt, I just did and I get different answers does that mean they're not?

their gradients need to be negative recipricles of each other to be perpendicular.

Reply 9

davros

Original post by mnot

their gradients need to be negative recipricles of each other to be perpendicular.

I think you mean reciprocals for anyone trying to google this :smile:

Reply 10

Melvin Guna

Original post by Kakakaty

Anyone know?

hint: the Tan theta1 and Tan theta 2 has a relationship for perpendicular lines

Reply 11

username5118974

Original post by Melvin Guna

hint: the Tan theta1 and Tan theta 2 has a relationship for perpendicular lines

I'm not too sure what this means, could you explain some more?

Reply 12

Melvin Guna

Original post by Kakakaty

I'm not too sure what this means, could you explain some more?

So the slope of one line is Tan theta 1 and the other is Tan theta 2. The product of the values of these slopes has to equal -1 for the lines to be perpendicular. You can calculate both Tan theta values by counting the boxes since they are the same size

(edited 3 years ago)

Reply 13

mqb2766

Original post by Kakakaty

You must realise line B has a negative gradient as it goes down.
Also the gradient of line A is < 1.

Reply 14

username5118974

Original post by mqb2766

You must realise line B has a negative gradient as it goes down.
Also the gradient of line A is < 1.

I'm not sure what else to do, I keep getting the same answer of A = 3 and for B = 2.5

Reply 15

Always_Confused

Hello! For each line, work out the equation of the line in the form y = mx + c, where m is your gradient, c is your y intercept.
For A: You can see in the graph your y intercept is 4. Pick a point on the line that is clear i.e (6,6) and sub these numbers in for y and x. Rearrange to calculate m(a).
For B: Your Y intercept is 10. Do the same for a point that lies on B. (2,5) for example. Rearrange to calculate m(b)

Does m(a) x m(b) = -1?
If yes, they are perpendicular
If no, they're not