If we draw a square from the center of the large circle to the center of one of the small circles, we can see that the sides of the square are equal to the radius of the small circle (see attached diagram)

Let r = the radius of the small circle

Using Pythagoras' Theorem $a^2+b^2=c^2$

(where a and b are the legs, and c is the hypotenuse, of a right triangle)

to find the diagonal of the square:

$\implies r^2 + r^2 = c^2$

$\implies 2r^2 = c^2$

$\implies c=\sqrt{2r^2}$

So the diagonal of the square = $\sqrt{2r^2}$

We are told that the radius of the large circle is 1:

⇒ Diagonal of square + r = 1

$\implies \sqrt{2r^2}+r=1$

$\implies \sqrt{2r^2}=1-r$

$\implies 2r^2=(1-r)^2$

$\implies 2r^2=1-2r+r^2$

$\implies r^2+2r-1=0$

Using the quadratic formula to calculate r:

$\implies r=\dfrac{-b\pm\sqrt{b^2-4ac}}{2a}$

$\implies r=\dfrac{-2\pm\sqrt{2^2-4(1)(-1)}}{2(1)}$

$\implies r=\dfrac{-2\pm\sqrt{8}}{2}$

$\implies r=-1\pm\sqrt{2}$

As distance is positive, $r=-1+\sqrt{2}=\sqrt{2}-1$ only

5 0

3 years ago

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What is an equation of the line that passes through the points (4, 4) and (8, 1)?

geniusboy [140]

Answer: y = -3/4x + 7

Step-by-step explanation:

first find slope:

y2-y1 / x2 - x1

1-4 / 8-4

-3/4

now just plug the slope (m) into the equation of a line using one of the points to find the y intercept

ill use (8,1)

1 = (-3/4)(8) + b

now solve :)

1 = -6 + b

7 = b

so now plug in the slope and the y intercept into the slope intercept form to find the equation of the line

y = -3/4x + 7

3 0

3 years ago

What is the total surface area of the square pyramid? ​

What is the total surface area of the square pyramid?