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1 year ago

What’s the error in these equations with steps will give Brainily

Mathematics

1 answer:

wlad13 [49]1 year ago

5 0

Answer:

2. (3+4) should be (3*4)

3. x is also x^1, so it should be x^(6+3+1)

4. you have to do 3^4 and 2^3 before timing them together

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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

6 hundreth = thousandths

ryzh [129]

60 hope it helps and its right

8 0

3 years ago

A student took a system of equations, multiplied the first equation by 2 and the second equation by 3, then added the results to

egoroff_w [7]

Answer:

system 4.

Step-by-step explanation:

3x+6y=9

multiply by 2

6x+12y=18 ....(1)

-2x+-4y=4

multiply by 3

-6x-12y=12 ...(2)

add (1) and (2)

0+0=30

which is impossible .It has no solutions.

3 0

2 years ago

Divide

saw5 [17]

I hope i dont any mistake :p tell me if u dont understand :)

7 0

2 years ago

Why it take much longer time ghan the time calculated

mrs_skeptik [129]

Answer:

for what bro

Step-by-step explanation:

please mark me as brainlest

3 0

2 years ago

Read 2 more answers