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4 years ago

Complete the identity. sin4x - cos4x = ?

Mathematics

2 answers:

xenn [34]4 years ago

5 0

Answer:

1-2cos^2x

Step-by-step explanation:

I took the test and got it correct

Katyanochek1 [597]4 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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Make x the subject of the following: b = x - 5

nevsk [136]

B=x-5
To get x on its own you have to add 5 to both sides. This gives you:
b+5=x
or
x=b+5

8 0

4 years ago

An architect wants to draw a rectangle with a diagonal of 13 centimeters. The length of the rectangle is to be 3 centimeters mor

butalik [34]

Answer:

The rectangle is 3.2 cm by 12.6 cm

Step-by-step explanation:

See attached image for a diagram.

Choose w to represent the width because the length is described by referring to the width: it's 3 more than (add 3) triple (multiplied by 3) the width.

Length = 3w + 3

The diagonal forms two right triangles, each with leg = w, other leg = 3w + 3, hypotenuse = 13.

The Pythagorean Theorem says $(\text{leg})^2+(\text{leg})^2=(\text{hypotenuse})^2$ so

$w^2+(3w+3)^2=13^2\\\\w^2+9w^2+18w+9=169\\\\10w^2+18w-160=0\\\\5w^2+9w-80=0\\$

Now solve using the Quadratic Formula with $a=5,\,b=9,\,c=-80$ .

$w=\frac{-b\pm\sqrt{b^2-4ac}}{2a}\\w=\frac{-9\pm\sqrt{81+1600}}{10}\\\\w=\frac{-9\pm\sqrt{1681}}{10}\\\\w=\frac{-9\pm41}{10}\\\\w=-5\text{ or }w=3.2$

The negative root makes no sense as a distance, so the width of the rectangle is 3.2 cm. The length is 3(3.2) + 3 = 12.6 cm.

5 0

3 years ago

Complete the transformations below. Then enter the final coordinates of the figure.

9966 [12]

Answer:

Step-by-step explanation:

If a point (x, y) is translated by 4 units horizontally right and 1 unit upwards, coordinates of the image point will be,

(x, y) → (x + 4. y + 1)

Therefore, vertices of the image triangle ABC will be,

A(2, 2) → A'(2+4, 2+1)

→ A'(6, 3)

B(5, -1) → B'(5+4, -1+1)

→ B'(9, 0)

C(1, -2) → C'(1+4, -2+1)

→ C'(5, -1)

Then reflected across y-axis.

Rule for the reflection across y-axis will be,

(x, y) → (-x, y)

A'(6, 3) → A"(-6, 3)

B'(9, 0) → B"(-9, 0)

C'(5, -1) → C"(-5, -1)

7 0

3 years ago

81 + 2d > 90, d = 2 TRUE OR FALSE

telo118 [61]

Answer:

False

Step-by-step explanation:

False because you plug in 2 for d and makes the equation 81 + 2x2 > 90 then it`s just simple math 2x2 is 4 making it 81 + 4 > 90 and the answer is 85 > 90 which is false

4 0

4 years ago

Simplify 2⅓+2⅔×1⅛ Pls solve it

ikadub [295]

Answer:

5 1/3

Step-by-step explanation:

2 1/3+(2 2/3) (1 1/8)= 5 1/3

4 0

4 years ago