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3 years ago

Complete the identity. sin4x - cos4x = ?

Mathematics

2 answers:

xenn [34]3 years ago

5 0

Answer:

1-2cos^2x

Step-by-step explanation:

I took the test and got it correct

Katyanochek1 [597]3 years ago

4 0

Since sin(2x)=2sinxcosx, we can plug that in to get sin(4x)=2sin(2x)cos(2x)=2*2sinxcosxcos(2x)=4sinxcosxcos(2x). Since cos(2x) = cos^2x-sin^2x, we plug that in. In addition, cos4x=cos^2(2x)-sin^2(2x). Next, since cos^2x=(1+cos(2x))/2 and sin^2x= (1-cos(2x))/2, we plug those in to end up with 4sinxcosxcos(2x)-((1+cos(2x))/2-(1-cos(2x))/2)
=4sinxcosxcos(2x)-(2cos(2x)/2)=4sinxcosxcos(2x)-cos(2x)
=cos(2x)*(4sinxcosx-1). Since sinxcosx=sin(2x), we plug that back in to end up with cos(2x)*(4sin(2x)-1)

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Step-by-step explanation:

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3 years ago

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Solve. 4 – d < 4 + d d > 8 d > 0 d > –8 d > –4

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Answer:

-2d + 4 < 4

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3 years ago

Four glasses of milk and 2 snack bars have a total of 72 carbohydrates (carbs), and 2 glasses of milk and 3 snack bars have a t

Travka [436]

One glass of milk has 11 carbs and one snack bar has 14 carbs.

Step-by-step explanation:

Let,

Glass of milk = x

Snack bar = y

According to given statement;

4x+2y=72 Eqn 1

2x+3y=64 Eqn 2

Multiplying Eqn 2 by 2

$2(2x+3y=64)\\4x+6y=128\ \ \ Eqn\ 3$

Subtracting Eqn 1 from Eqn 3

$(4x+6y)-(4x+2y)=128-72\\4x+6y-4x-2y=56\\4y=56$

Dividing both sides by 4

$\frac{4y}{4}=\frac{56}{4}\\y=14$

Putting y=14 in Eqn 1

$4x+2(14)=72\\4x+28=72\\4x=72-28\\4x=44$

Dividing both sides by 4

$\frac{4x}{4}=\frac{44}{4}\\x=11$

One glass of milk has 11 carbs and one snack bar has 14 carbs.

Keywords: linear equations, subtraction

Learn more about linear equations at:

#LearnwithBrainly

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3 years ago

How do you find the percent of a number?

Tom [10]

Answer:

(hope this helps can i plz have brainlist :D hehe)

Step-by-step explanation:

How to Calculate Percentages

There are many formulas for percentage problems. You can think of the most basic as X/Y = P x 100. The formulas below are all mathematical variations of this formula.

Let's explore the three basic percentage problems. X and Y are numbers and P is the percentage:

Find P percent of X

Find what percent of X is Y

Find X if P percent of it is Y

Read on to learn more about how to figure percentages.

1. How to calculate percentage of a number. Use the percentage formula: P% * X = Y

Example: What is 10% of 150?

Convert the problem to an equation using the percentage formula: P% * X = Y

P is 10%, X is 150, so the equation is 10% * 150 = Y

Convert 10% to a decimal by removing the percent sign and dividing by 100: 10/100 = 0.10

Substitute 0.10 for 10% in the equation: 10% * 150 = Y becomes 0.10 * 150 = Y

Do the math: 0.10 * 150 = 15

Y = 15

So 10% of 150 is 15

Double check your answer with the original question: What is 10% of 150? Multiply 0.10 * 150 = 15

2. How to find what percent of X is Y. Use the percentage formula: Y/X = P%

Example: What percent of 60 is 12?

Convert the problem to an equation using the percentage formula: Y/X = P%

X is 60, Y is 12, so the equation is 12/60 = P%

Do the math: 12/60 = 0.20

Important! The result will always be in decimal form, not percentage form. You need to multiply the result by 100 to get the percentage.

Converting 0.20 to a percent: 0.20 * 100 = 20%

So 20% of 60 is 12.

Double check your answer with the original question: What percent of 60 is 12? 12/60 = 0.20, and multiplying by 100 to get percentage, 0.20 * 100 = 20%

3. How to find X if P percent of it is Y. Use the percentage formula Y/P% = X

Example: 25 is 20% of what number?

Convert the problem to an equation using the percentage formula: Y/P% = X

Y is 25, P% is 20, so the equation is 25/20% = X

Convert the percentage to a decimal by dividing by 100.

Converting 20% to a decimal: 20/100 = 0.20

Substitute 0.20 for 20% in the equation: 25/0.20 = X

Do the math: 25/0.20 = X

X = 125

So 25 is 20% of 125

Double check your answer with the original question: 25 is 20% of what number? 25/0.20 = 125

Remember: How to convert a percentage to a decimal

Remove the percentage sign and divide by 100

15.6% = 15.6/100 = 0.156

Remember: How to convert a decimal to a percentage

Multiply by 100 and add a percentage sign

0.876 = 0.876 * 100 = 87.6%

(hope this helps can i plz have brainlist :D hehe)

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2 years ago

Read 2 more answers