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3 years ago

Iodine-125 has a half-life of about 60 days.

1 answer:

4 0

We know that Iodine - 125 has a half life of 60 days.
300 : 60 = 5 . It means that it was halved 6 times.
Therefore: 500 mg * 0.5^5 =
= 500 mg * 0.5 * 0.5 * 0.5 * 0.5 * 0.5 =
= 500 mg * 0.03125 = 15.625 mg
Answer: 3. 15.625 mg.

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If tanA+sinA=m and tanA-sinA=n.prove that m^2-n^2=4√mn

mash [69]

Let $a=\tan A$ and $b=\sin A$ . Then

$m^2-n^2=(a+b)^2-(a-b)^2=(a^2+2ab+b^2)-(a^2-2ab+b^2)=4ab$

$\implies m^2-n^2=4\tan A\sin A$

and

$mn=(a+b)(a-b)=a^2-b^2$

$\implies4\sqrt{mn}=4\sqrt{\tan^2A-\sin^2A}$

The expression under the square root can be rewritten as

$\tan^2A-\sin^2A=\dfrac{\sin^2A}{\cos^2A}-\sin^2A=\sin^2A\left(\dfrac1{\cos^2A}-1\right)=\sin^2A(\sec^2A-1)$

Recall that

$\sin^2A+\cos^2A=1\implies\tan^2A+1=\sec^2A$

so that

$\tan^2A-\sin^2A=\sin^2A\tan^2A$

and assuming $\sin A>0$ and $\tan A>0$ , we end up with

$4\sqrt{\tan^2A-\sin^2A}=4\tan A\sin A$

so that

$m^2-n^2=4\sqrt{mn}$

as required.

5 0

3 years ago

Solve log base 2 of one over thirty two.

SSSSS [86.1K]

It’s in this picture:)

8 0

3 years ago

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It is estimated 30% of all adults in United States invest in stocks and that 84% of U.S. adults have investments in fixed

lana66690 [7]

Answer:

=109%

Step-by-step explanation:

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3 years ago

Direct Variation.<br>¯\_(ツ)_/¯

Alekssandra [29.7K]

Answer:

y = 1/6

Step-by-step explanation:

direct variation

y =kx

substitute in what we know to find k

1/2 = k*3

solve for k

divide by 3

1/2 /3 = k

1/6 = k

substitute k into the direct variation equation

y = 1/6 x

let x = 1

y = 1/6 *1

y = 1/6

5 0

3 years ago

Johan's water bottle holds 4.2L of water. Johan has drank 51% of water in the bottle. How much, in litres, has he drunk?

swat32

Answer : 2.142L

Step-by-step explanation:

51/100 × 4.2

=51/100 × 42/10

= 2142/1000

= 2.142L

8 0

3 years ago

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