Silly Questions Thread

[Aqualim]

ok thanks.. This is a follow up question;

Find the magnitude of BAC in degrees correct to one decimal place if A=(-8,2), B=(-6,10) and C=(4,11)

Anyone?

[the.watchman]

Gradient of AB:



Gradient of AC:



So the angle

[Aqualim]

Cheer mate, quick question regarding the working out process.

Do you take AB away from AC because the question is asking for the magnitude of BAC (hence B is before C)?

And also, is there a way to verify this on the cas calculator?
I've drawn both graphs on the Graphs page and have found an 'angle' option, but where on the two straight lines am I finding the angle? lol stupid question I know

[the.watchman]

Cheer mate, quick question regarding the working out process.

Do you take AB away from AC because the question is asking for the magnitude of BAC (hence B is before C)?

And also, is there a way to verify this on the cas calculator?
I've drawn both graphs on the Graphs page and have found an 'angle' option, but where on the two straight lines am I finding the angle? lol stupid question I know

No, I used the one with a greater gradient first, because the angle it makes with the positive x-direction is larger

To check it on a graphics, click any point on AB (to the right of the intersection), then the intersection point, then move the cursor around to find the angle

[Aqualim]

Cheer mate, quick question regarding the working out process.

Do you take AB away from AC because the question is asking for the magnitude of BAC (hence B is before C)?

And also, is there a way to verify this on the cas calculator?
I've drawn both graphs on the Graphs page and have found an 'angle' option, but where on the two straight lines am I finding the angle? lol stupid question I know

No, I used the one with a greater gradient first, because the angle it makes with the positive x-direction is larger

To check it on a graphics, click any point on AB (to the right of the intersection), then the intersection point, then move the cursor around to find the angle

So does that mean in general we should use the one with the greater gradient? (assuming we are finding the positive gradient)

[the.watchman]

Cheer mate, quick question regarding the working out process.

Do you take AB away from AC because the question is asking for the magnitude of BAC (hence B is before C)?

And also, is there a way to verify this on the cas calculator?
I've drawn both graphs on the Graphs page and have found an 'angle' option, but where on the two straight lines am I finding the angle? lol stupid question I know

No, I used the one with a greater gradient first, because the angle it makes with the positive x-direction is larger

To check it on a graphics, click any point on AB (to the right of the intersection), then the intersection point, then move the cursor around to find the angle

So does that mean in general we should use the one with the greater gradient? (assuming we are finding the positive gradient)

I think so, that's how I would do it
But then if it's negative gradient, then the least negative (greatest? ) gradient first maybe?

[TrueTears]

or.... Sketch the graph and see! A quick sketch neva hurts

[the.watchman]

or.... Sketch the graph and see! A quick sketch neva hurts

Nice!

[Aqualim]

Is this question solveable without a calculator?

Using and , sketch on the same set of axes. Hence sketch the graph of on the same graph

[the.watchman]

Is this question solveable without a calculator?

Using and , sketch on the same set of axes. Hence sketch the graph of on the same graph

Yeah, sketch both on the same axes, find major points (eg. zeros, squares etc.) and join the dots with a smooth curve

[the.watchman]

Is this question solveable without a calculator?

Using and , sketch on the same set of axes. Hence sketch the graph of on the same graph

Yeah, sketch both on the same axes, find major points (eg. zeros, squares etc.) and join the dots with a smooth curve

On second thoughts, don't do that, just dilate by a factor of from the x-axis

[Aqualim]

Got another question;

When finding equations for exponential modelling, how do you know when and when not to include the irrational variable ''?

In some questions I have had, you are required to have an in the formula, whereas others I wasn't required to.

[GerrySly]

As in Eulers number ? Post up examples of what you mean...

[Aqualim]

Yes Eulers number 'e'.

Example;
A highly volatile substance initially has a mass of 1200 g and its mass is reduced by 12% each second.

1) Write a formula that gives the mass of the substance (m) at time (t) seconds.

Why isn't Euler's number included in this formula, whereas the standard equation for growth or decay is

[GerrySly]

Get two points so you can sub them in (and for some checking) and





Doing a quick check with our previous points, .

So it does include but in your workings it gets cancelled out. If it includes any exponential growth, start with that formula and just move through it (maybe cancelling out maybe not)