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Nina [5.8K]
4 years ago
9

If the first 100 elements on the periodic table, 13/100 were discovered in the ancient times, and 21/100 were discovered in the

Middle Ages. Another 5/10 were discovered in the 1800s. What fraction of the first 100 elements was discovered after the 1800s? Explain.
Mathematics
1 answer:
Inessa05 [86]4 years ago
5 0

Answer:

\frac{61}{100} , 61/100

Step-by-step explanation:

First we need to add all of the fractions before or at the 1980s, they have the same denominator, so we simply just add. It comes out to 39/100. Subtract 39 from 100 and we get 61 out of 100 or 61/100 or 61%.

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Trigonometric question, 30 points, will give brainliest.
zheka24 [161]

hmmm first off let's convert the √3 +i to trigonometric form, and then use De Moivre's root theorem, bearing in mind that √3 and i or 1i are both positive, meaning we're on the I Quadrant.

\bf (\stackrel{a}{\sqrt{3}}~,~\stackrel{b}{1i})\qquad \begin{cases} r=&\sqrt{(\sqrt{3})^2+1^2}\\ &\sqrt{3+1}\\ &2\\ \theta =&tan^{-1}\left( \frac{1}{\sqrt{3}}\right)\\\\ &tan^{-1}\left( \frac{\sqrt{3}}{3} \right)\\ &\frac{\pi }{6} \end{cases}~\hfill \implies ~\hfill 2\left[ cos\left( \frac{\pi }{6}\right) +i~sin\left( \frac{\pi }{6}\right) \right]

\bf ~\dotfill\\\\ \qquad \textit{power of two complex numbers} \\\\\ [\quad r[cos(\theta)+isin(\theta)]\quad ]^n\implies r^n[cos(n\cdot \theta)+isin(n\cdot \theta)] \\\\[-0.35em] ~\dotfill

\bf \left[ 2\left[ cos\left( \frac{\pi }{6}\right) +i~sin\left( \frac{\pi }{6}\right) \right] \right]^3\implies 2^3\left[ cos\left( 3\cdot \frac{\pi }{6}\right) +i~sin\left( 3\cdot \frac{\pi }{6}\right) \right] \\\\[-0.35em] \rule{34em}{0.25pt}\\\\ ~\hfill 8\left[cos\left( \frac{\pi }{2} \right) +i~sin\left( \frac{\pi }{2} \right) \right]~\hfill

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4 years ago
A 4 inch by 6 inch picture is placed in a frame that creates a uniform border of x inches around the picture. The area of the en
HACTEHA [7]

The complete question is

"A 4 inch by 6 inch picture is placed in a frame that creates a uniform border of x inches around the picture. The area of the entire frame (including where the picture is placed) is equal to 55.25 square inches.

What will be the width and length of the frame?"

The width of the frame is 4+2x, and the length of the frame is 6+2x.

<h3>What is the area of the rectangle?</h3>

The area of the rectangle is the product of the length and width of a given rectangle.

The area of the rectangle = length × Width

We know that the picture is 4 inches wide and 6 inches long.

Since there is a uniform border of x inches around the picture, so we must add 2x inches to each dimension.

The area will be = (4+2x)(6+2x) = 55.25

Therefore, the width of the frame is 4+2x, and the length of the frame is 6+2x.

Learn more about the area;

brainly.com/question/1658516

#SPJ1

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