# help

• Jun 15th 2008, 06:20 AM
santatrue
help
1.Determine the maximum area of a triangle that has a hypotenuse of 5 m.[/FONT][/COLOR]

2.Determine the local maxima and local minima of the function sinx^3 +cosx^3 for (0,2pie)

3. Two sides of a triangle have lengths of 1 m and 2 m. The angle between them is increasing at $\displaystyle pie$/1000 rad/s.Determine the rate of change of the third side when the angle between the first two sides is pie/4
• Jun 15th 2008, 06:25 AM
kalagota
Quote:

Originally Posted by santatrue
[FONT='Cambria','serif']1.Determine the maximum area of a triangle that has a hypotenuse of 5 m.[/font]

[FONT='Cambria','serif']2.[FONT='Cambria','serif']Determine the local maxima and local minima of the function sinx^3 +cosx^3 [FONT='Cambria','serif'] for (0,2pie)[/font][/font][/font]
[FONT='Cambria','serif'][FONT='Cambria','serif']Two sides [/font]
[FONT='Cambria','serif']Two sides 3. Two sides of a triangle have lengths of 1 m and 2 m. The angle between them is increasing at $\displaystyle pie$/1000 rad/s.Determine[/font]
[FONT='Cambria','serif']Determine the rate of change of the third side when the angle between the first two sides is pie/4[/font]
[/font]

these are applications of first and second derivative tests.. why don't you give us what you have done so far and we'll check it for you..
• Jun 15th 2008, 07:45 AM
santatrue
Quote:

Originally Posted by kalagota
these are applications of first and second derivative tests.. why don't you give us what you have done so far and we'll check it for you..

of course i tried my best but cannot get to any answer

would be great if you could help me instead of taunting me for my incapablity
• Jun 15th 2008, 07:48 AM
Moo
Hi

Quote:

Originally Posted by santatrue
of course i tried my best but cannot get to any answer

would be great if you could help me instead of taunting me for my incapablity

I don't think he was taunting you o.O

For the first exercise, let x be one of the sides of the triangle.
Then, express the length of the third side with respect to the hypotenuse and x, using the Pythagorean theorem.
--> area=x*(third side)/2=...a function of x...

Edit : this is my 22:):)th post ^^
• Jun 15th 2008, 09:07 AM
santatrue
Quote:

Originally Posted by Moo
Hi

I don't think he was taunting you o.O

For the first exercise, let x be one of the sides of the triangle.
Then, express the length of the third side with respect to the hypotenuse and x, using the Pythagorean theorem.
--> area=x*(third side)/2=...a function of x...

Edit : this is my 22:):)th post ^^

sorry but i m still unable to continue after that

i need many help even for the other questions
• Jun 15th 2008, 09:19 AM
topsquark
Quote:

Originally Posted by santatrue
1.Determine the maximum area of a triangle that has a hypotenuse of 5 m.[/font][/color]

I'm assuming since we have the word "hypotenuse" we are dealing with a right triangle. So assume this right triangle has legs a and b. Then by the Pythagorean theorem we know that
$\displaystyle a^2 + b^2 = 25$

$\displaystyle b = \sqrt{25 - a^2}$

The area of this triangle is
$\displaystyle A = \frac{1}{2}ab = \frac{1}{2}a \sqrt{25 - a^2}$

Use the first derivative to find the value of a that corresponds to the maximum area.

-Dan