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3 years ago

Is this right 20 points!!!

Mathematics

1 answer:

Mars2501 [29]3 years ago

5 0

Answer:

Brailniest

Step-by-step explanation:

0.25k+1.5-k-3.5

-0.75k-2

so you are right

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Rewrite with only sin x and cos x.

Annette [7]

Option A

$\cos 3 x=\cos x-4 \cos x \sin ^{2} x$

<em><u>Solution:</u></em>

Given that we have to rewrite with only sin x and cos x

Given is cos 3x

$cos 3x = cos(x + 2x)$

We know that,

$\cos (a+b)=\cos a \cos b-\sin a \sin b$

Therefore,

$\cos (x+2 x)=\cos x \cos 2 x-\sin x \sin 2 x$ ---- eqn 1

We know that,

$\sin 2 x=2 \sin x \cos x$

$\cos 2 x=\cos ^{2} x-\sin ^{2} x$

Substituting these values in eqn 1

$\cos (x+2 x)=\cos x\left(\cos ^{2} x-\sin ^{2} x\right)-\sin x(2 \sin x \cos x)$ -------- eqn 2

We know that,

$\cos ^{2} x-\sin ^{2} x=1-2 \sin ^{2} x$

Applying this in above eqn 2, we get

$\cos (x+2 x)=\cos x\left(1-2 \sin ^{2} x\right)-\sin x(2 \sin x \cos x)$

$\begin{aligned}&\cos (x+2 x)=\cos x-2 \sin ^{2} x \cos x-2 \sin ^{2} x \cos x\\\\&\cos (x+2 x)=\cos x-4 \sin ^{2} x \cos x\end{aligned}$

$\cos (x+2 x)=\cos x-4 \cos x \sin ^{2} x$

Therefore,

$\cos 3 x=\cos x-4 \cos x \sin ^{2} x$

Option A is correct

7 0

3 years ago

In the month of June, the temperature in Johannesburg, South Africa, varies over the day in a periodic way that can be modeled a

Art [367]

Answer:

The answer is " $\bold{T = - 7.5 \cos \frac{\pi}{12}( t - 4 )+ 10.5}$ "

Step-by-step explanation:

Given value:

Temp-maximum= $18^{\circ}$

Temp. minimum = $3^{\circ}$

It is halfway between 10 am and 10 pm to 4 am.

The sinus and cosine roles could be used throughout the year to predict fluctuations in climate models. Its type of formula that can be used to model such information is:

$T = A \cos B(t-C) + D,$ where parameters are A, B , C, D, T is the ° C temperature and t is the time (1-24)

$A = amplitude = \frac{(T_{max} - T_{min})}{2}\\\\$

$= \frac{(3 - 18)}{2}\\\\= - \frac{15}{2}\\\\ = -7.5$

$B = \frac{2 \pi}{24}\\\\$

$= \frac{\pi}{12}$

$C = \text{ units translated to the right}= 4$

$D = y_{min} + amplitude = units \ translated \ up\\\\$

D = 7.5 + 3 = 10.5

Its trigonometric function equation that model temperature T hours after midnight in Johannesburg t.

$T = - 7.5 \cos \frac{\pi}{12}( t - 4 )+ 10.5$

6 0

4 years ago

What’s the answer too this problem I can’t solve?

emmasim [6.3K]

I'm using PEDMAS.

Multiplication first.

2 • 4 = 8

Subtraction.

20 - 4 = 16

16 + 8 = 24

Please let me know if you spot any errors (especially the fraction operation)

4 0

3 years ago

Why is it so expensive to buy organic food

Jet001 [13]

A few reasons are:
1) They contain very little to no chemicals
2) It takes more work to grow, care for, and harvest
3) Majority of farmers produce organic food as a living so it has to be more expensive if they actually want to make a profit

6 0

3 years ago

Can you help me I will give you brainiest answer

Gemiola [76]

The first one is 20 and the second one is 19 and the third one is 25 and the fourth one is 15 and the fifth one is 11 and the sixth one is 28

5 0

2 years ago