Help Please (1 Viewer)

[Aznmichael92]

I need help with this question so can anyone help me?

The question is:

A rectangle has a perimeter of 40 cm and a length of x cm.

1) Show that the area is given by A=20x - x^2

thanks

 

[lyounamu]

I need help with this question so can anyone help me?

The question is:

A rectangle has a perimeter of 40 cm and a length of x cm.

1) Show that the area is given by A=20x - x^2

thanks

A rectangle is a parallelogram with 4 angles that are 90 degrees each.

Since it is a parallologram, the opposite sides are equal.

Let the sides be x, x, y and y (x and x are opposite to each other and y and y are opposite to each other)

Therefore, P = 2x + 2y
i.e. 40 = 2x + 2y
2y = 40-2x
y = 20 - x

The area of a rectangle is given by A = bh where b = x and h = y
A = xy
= x . (20-x)
= 20x - x^2

 

[Aznmichael92]

A rectangle is a parallelogram with 4 angles that are 90 degrees each.

Since it is a parallologram, the opposite sides are equal.

Let the sides be x, x, y and y
Therefore, P = 2x + 2y
i.e. 40 = 2x + 2y
2y = 40-2x
y = 20 - x
A = xy
= x . (20-x)
= 20x - x^2

thank you thank you u r pro

You should really start to tutor people, I bet so many people on BOS will want to learn from you

 

[Aznmichael92]

Also this question please.

Given Sin@ = 12/13 and Tan@ < 0, find Cos@

thanks

 

[lyounamu]

Also this question please.

Given Sin@ = 12/13 and Tan@ < 0, find Cos@

thanks

I sent you the mail with the answer just then.

 

[lyounamu]

thank you thank you u r pro

You should really start to tutor people, I bet so many people on BOS will want to learn from you

No. I am not really good enough yet. I am really good at Mathematics but I lack so many skills in Mathematics Extension 1. I need to revise more. I didn't spend any for Mathematics Extension 1 until today.

 

[Aznmichael92]

I sent you the mail with the answer just then.

thank you thank you so much

Maybe you should be my tutor. Or maybe I should consider you my idol

 

[Aerath]

Maybe you should be my tutor. Or maybe I should consider you my idol

To many people, he already is.

 

[Aznmichael92]

To many people, he already is.

noooo, u stealing ny tutor

I actually realise that the two questions I asked were not that difficult. I guess I was brain dead or needed someone(namu) to lead me the way to solving the problem.

 

[lyounamu]

I am not that good. Only subject that I might be really good at is Mathematics & Business Studies. (just Mathematics, not Mathematics Extension 1, lol)

 

[bored of sc]

Also this question please.

Given Sin@ = 12/13 and Tan@ < 0, find Cos@

thanks

Tan @ = -12/5, Cos @ = -5/13, I hope that is right!

 

[Aerath]

Yup, cos@ is -5/13

 

[bored of sc]

More important I think is the working out.

Using the common pythagorean triad of 5,12,13: the adjacent side came out as 5 units (adjacent side = square root ( 13² - 12² ).

Opposite side = 12

Hypotenuse side = 13

Adjacent side = 5

Sin @ = opp/hyp = 12/13

Cos @ = adj/hyp = 5/13

Tan @ = opp/adj = 12/5

Since sin is positive (12/13) and tan is negative (<0), the triangle is in the 2nd quadrant (the only quadrant where sin is positive and tan is negative). Therefore, using ASTC, sin is the only positive result in the second quadrant, therfore cos @ = -5/13.

Is that the right working out?

 

[lyounamu]

More important I think is the working out.

Using the common pythagorean triad of 5,12,13: the adjacent side came out as 5 units (adjacent side = square root ( 13² - 12² ).

Opposite side = 12

Hypotenuse side = 13

Adjacent side = 5

Sin @ = opp/hyp = 12/13

Cos @ = adj/hyp = 5/13

Tan @ = opp/adj = 12/5

Since sin is positive (12/13) and tan is negative (<0), the triangle is in the 2nd quadrant (the only quadrant where sin is positive and tan is negative). Therefore, using ASTC, sin is the only positive result in the second quadrant, therfore cos @ = -5/13.

Is that the right working out?

Yeah. Your working out is right.

By the way, that's the working out I sent to Aznmichael yesterday. You didn't have to do it.

 

[bored of sc]

Yeah. Your working out is right.

By the way, that's the working out I sent to Aznmichael yesterday. You didn't have to do it.

Don't worry, I love maths. It was fun doing it as I am sure it was for you too.

 

[lyounamu]

Don't worry, I love maths. It was fun doing it as I am sure it was for you too.

That's great to hear that there is someone like I am.

 

[Forbidden.]

I reckon physics is better.
It made maths more interesting.