Need help with this 4, 5, 6

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

6 radians is the same as what degree

olya-2409 [2.1K]

$1~radian=\frac{180}{\pi}degrees\\\\1~degree=\frac{\pi}{180}radians$

8 0

3 years ago

Read 2 more answers

Write three factors if algebraic term 5k

ExtremeBDS [4]

5, k, 5k................

5 0

3 years ago

Read 2 more answers

(y+1/x)^(x+y)*(x-1/y)^(x+y)÷{(x^2-1/y^2)^x*(y^2-1/x^2)^y}<br>

Yuki888 [10]

Answer:

is it right question or not tell me and I will solve it

6 0

3 years ago

Read 2 more answers

Which is one of the transformations applied to the graph of f(x) = x2 to change it into the graph of g(x) = 9x2 – 36X?

Fiesta28 [93]

Assuming I understand your question correctly, in that you’re looking for just some descriptions of the differences between the functions. If so, then I’d say:

First graph both functions, the f(x) and the g(x). Then spot the differences.
Note that the g(x) function has shifted towards the right compared with the f(x) function.
Another way that the g(x) differs from the f(x) function is that it’s stretched. The vertex is in the IV quadrant for g(x) rather than at the origin for f(x).

I hope that helps.

5 0

3 years ago

Read 2 more answers