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If 180° < α < 270°, cos⁡ α = −817, 270° < β < 360°, and sin⁡ β = −45, what is cos⁡ (α + β)?

eduard

Answer:

$cos(\alpha+\beta)=-\frac{84}{85}$

Step-by-step explanation:

we know that

$cos(\alpha+\beta)=cos(\alpha)*cos(\beta)-sin(\alpha)*sin(\beta)$

Remember the identity

$cos^{2} (x)+sin^2(x)=1$

step 1

Find the value of $sin(\alpha)$

we have that

The angle alpha lie on the III Quadrant

so

The values of sine and cosine are negative

$cos(\alpha)=-\frac{8}{17}$

Find the value of sine

$cos^{2} (\alpha)+sin^2(\alpha)=1$

substitute

$(-\frac{8}{17})^{2}+sin^2(\alpha)=1$

$sin^2(\alpha)=1-\frac{64}{289}$

$sin^2(\alpha)=\frac{225}{289}$

$sin(\alpha)=-\frac{15}{17}$

step 2

Find the value of $cos(\beta)$

we have that

The angle beta lie on the IV Quadrant

so

The value of the cosine is positive and the value of the sine is negative

$sin(\beta)=-\frac{4}{5}$

Find the value of cosine

$cos^{2} (\beta)+sin^2(\beta)=1$

substitute

$(-\frac{4}{5})^{2}+cos^2(\beta)=1$

$cos^2(\beta)=1-\frac{16}{25}$

$cos^2(\beta)=\frac{9}{25}$

$cos(\beta)=\frac{3}{5}$

step 3

Find cos⁡ (α + β)

$cos(\alpha+\beta)=cos(\alpha)*cos(\beta)-sin(\alpha)*sin(\beta)$

we have

$cos(\alpha)=-\frac{8}{17}$

$sin(\alpha)=-\frac{15}{17}$

$sin(\beta)=-\frac{4}{5}$

$cos(\beta)=\frac{3}{5}$

substitute

$cos(\alpha+\beta)=-\frac{8}{17}*\frac{3}{5}-(-\frac{15}{17})*(-\frac{4}{5})$

$cos(\alpha+\beta)=-\frac{24}{85}-\frac{60}{85}$

$cos(\alpha+\beta)=-\frac{84}{85}$

4 0

3 years ago

In an area of the Great Plains, records were kept on the relationship between the rainfall (in inches) and the yield of wheat (b

vovikov84 [41]

Answer: D. 0.981

Step-by-step explanation:

Step 1: For the given data table on x^2

We square all values given to us

Step 2: we repeat Same for Y^2 table too.

Step 3: XY table we multiply x and y

Step 4: we make a summation of them all

Step 5: we input our summer value into our formula.

Step 6 : we arrive at our answer which is 0.981

7 0

3 years ago

Which number is the same distance away from -12 as 2?

Ray Of Light [21]

Answer:

-26

Step-by-step explanation:

2 is 14 away from -12. The other number that is 14 away from -12 is -26.

-12 + x = 2

x = 14

-12 - 14 = -26

4 0

2 years ago

What is HCF and LCM ? # confused

GaryK [48]

HCF= highest common factor
LCM= least common multiple

7 0

3 years ago

Read 2 more answers

What is the answer for number 8 and pls give step by step

Pie

Answer:

Trapezoid 1 (left side):

Base 1 = 2

Base 2 = 5

Trapezoid 2 (right side):

Base 1 = 6

Base 2 = 8

Step-by-step explanation:

1st trapezoid:

b_1 = x

b_2 = x + 3

h = 4

Hence, area (from formula) would be:

$A=\frac{h}{2}(b_1+b_2)\\A=\frac{4}{2}(x+x+3)\\A=2(2x+3)\\A=4x+6$

2nd trapezoid:

b_1 = 3x

b_2 = 4x

h = 2

Putting into formula, we get:

$A=\frac{h}{2}(b_1+b_2)\\A=\frac{2}{2}(3x+4x)\\A=1(7x)\\A=7x$

Let's equate both equations for area and find x first:

$4x+6=7x\\6=7x-4x\\6=3x\\x=\frac{6}{3}\\x=2$

We can plug in 2 into x and find length of each base of each trapezoid.

Trapezoid 1 (left side):

Base 1 = x = 2

Base 2 = x + 3 = 2 + 3 = 5

Trapezoid 2 (right side):

Base 1 = 3x = 3(2) = 6

Base 2 = 4x = 4(2) = 8

8 0

3 years ago