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lys-0071 [83]
3 years ago
15

Please solve the eqution Cos4x + cos2x - 2 =0

Mathematics
1 answer:
horrorfan [7]3 years ago
6 0

cos4x = cos2x

We know that:

cos2x = 1-2cos^2 x

==> cos4x = 1-2cos^2 (2x)

Now substitute:

==> 1-2cos^2 (2x) = cos2x

==> 2cos^2 (2x) + cos2x - 1 = 0

Now factor:

==> (2cos2x -1)(cos2x + 1) = 0

==> 2cos2x -1 = 0 ==> cos2x =1/2 ==> 2x= pi/3

==> x1= pi/6 , 7pi/6

==> x1= pi/6 + 2npi

==> x2= 7pi/6 + 2npi

==> cos2x = -1 ==> 2x= pi ==> x3 = pi/2 + 2npi.

<span>==> x= { pi/6+2npi, 7pi/6+2npi, pi/2+2npi}</span>

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What are natural numbers in a set less than 3
sergeinik [125]
Natural number are basically " counting numbers ". They have no decimals, no fractions, and no negative numbers. It is debated whether 0 is included.

so ur natural numbers less then 3 are {1,2 }...not 100% sure if u include 0. I do not think u do.
4 0
3 years ago
Help please i will give 30 points
Nata [24]

Answer:

C. 7h + 50 > 99

Step-by-step explanation:

She earns <u>more</u> than $99, so you know that the sign will be > (more than).

h is the number of hours, so to find how much she earns for working h hours at $7/hour, you multiply h by 7  ---  7h

She also earns an additional $50, which will be +50.

Therefore, the equation is: 7h + 50 > 99

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2 years ago
What is equivalent to 4.321 × 10−4 ?<br><br> What is equivalent to 4.321 × 10−4 ?
Arlecino [84]

Please write that as 4.321 × 10^(−4).  The " ^ " indicates exponentiation and the parentheses help make clear that your exponent here is a negative one.

Rewrite 4.321 × 10^(−4) by moving the decimal point 4 places to the left:

0.0004321

7 0
3 years ago
Please help thank you!
kotegsom [21]

Answer:

Note that PQ + QR = PR:

Once:  

PR = 15x-11\\PQ=3x+6

PQ + QR = PR\\\\(3x+6)+QR=(15x-11)\\\\QR=(15x-11)-(3x+6)\\\\QR=15x-11-3x-6\\\\QR=12x-17\\

Therefore, the answer is letter B

8 0
3 years ago
What is the y-intercept of y = -3x?
Greeley [361]

Answer:

( 0, 0 )

Step-by-step explanation:

In this equation, you can see that there is not y-intercept, and since there is no y-intercept, that means that it will be "0", and that the line goes straight to the origin ( 0, 0 )

Hope this helped!

Have a supercalifragilisticexpialidocious day!

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