Need help with two questions (1 Viewer)

[BlueGas]

 

[rand_althor]

For the first one: Use m=tan(x) to find the gradient of line l. Note that the gradient of line l is negative. Now, since lines l and k are perpendicular, what relationship exists between their gradients? Use this to find the gradient of line k.

For the second one: The correct answer is 2ln(4).

 

[BlueGas]

For the first one: Use m=tan(x) to find the gradient of line l. Note that the gradient of line l is negative. Now, since lines l and k are perpendicular, what relationship exists between their gradients? Use this to find the gradient of line k.

For the second one: The correct answer is 2ln(4).

I got the same answer, 2ln4 for the second question but there's no option for it.

 

[Flop21]

For the first one: Use m=tan(x) to find the gradient of line l. Note that the gradient of line l is negative. Now, since lines l and k are perpendicular, what relationship exists between their gradients? Use this to find the gradient of line k.

For the second one: The correct answer is 2ln(4).

Can someone explain m=tan(x)? How do you know which angle to use??

 

[Flop21]

I got the same answer, 2ln4 for the second question but there's no option for it.

I also got 2ln4.

What is this question from? Maybe it's a mistake?

 

[BlueGas]

I also got 2ln4.

What is this question from? Maybe it's a mistake?

It's from Baulkham Hills 2015 trial paper.

 

[rand_althor]

the integration of 2/x is lnx

It is 2ln(x)+C.

 

[Flop21]

the integration of 2/x is lnx

It is? I thought the integral of 1/x is lnx. Hence we take the 2 outside.

 

[nisak]

you have to use tan30 because we are trying to find the slope of line k. and then by using tan30 the answer is C

 

[nisak]

thats what i thought at first because I've done this past paper before and i know its 2lnx+C but the answer for the question is actually B. unless theres a mistake with the options

 

[BlueGas]

you have to use tan30 because we are trying to find the slope of line k. and then by using tan30 the answer is C

Why can't we use tan60?

 

[Flop21]

you have to use tan30 because we are trying to find the slope of line k. and then by using tan30 the answer is C

Still don't understand how you figure out to use 30.

 

[nisak]

Why can't we use tan60?

you use tan60 if you are trying to find the slope of line l

 

[BlueGas]

thats what i thought at first because I've done this past paper before and i know its 2lnx+C but the answer for the question is actually B. unless theres a mistake with the options

Well why is it B? What happens to the "2"?

 

[calamebe]

Can someone explain m=tan(x)? How do you know which angle to use??

The gradient of a line is equal to the gradient it makes with the x-axis in the positive direction. This is because tan(x) is opposite over adjacent, which is rise over run, so tan(x) is the gradient. In this case, the angle with the x-axis is not in the positive direction, so we make the gradient negative. Tan(60) is root(3), so the gradient of the line is - root(3), and then because they are perpendicular angles we take the negative reciprocal and we get 1/root(3).

And 2ln(4) is definitely the answer.

 

[nisak]

Well why is it B? What happens to the "2"?

the answers are wrong its 2ln4

 

[calamebe]

the answers are wrong its 2ln4

I think people are confused because you said the integral of 2/x is ln(x), when it should be 2ln(x).

 

[nisak]

I think people are confused because you said the integral of 2/x is ln(x), when it should be 2ln(x).

yeah sorry! i got confused myself because of the options, sorry guys!

 

[calamebe]

yeah sorry! i got confused myself because of the options, sorry guys!

It's cool we all make mistakes.