Question

Solve using the laws of cosine

Answer 1

Answer:

13°

Step-by-step explanation:

Cosine formula: a² = b² + c² - 2(b)(c)cos(a)

8² = 21² + 14² - 2(21)(14)cos(x)

64 = 441 + 196 - 588cos(x)

Bring constants to one side

64 = 441 + 196 - 588cos(x)

-441  -441  -196

-196

-573 = -588cos(x)

Divide by the coefficient

-573/-588 = -588cos(x)/-588

cos(x) = 573/588

To find x you need to use arcsin or cos^-1

x = arccos(573/588) = 12.969°

Answer 2

Answer:

$\displaystyle 13° = m∠X$

Step-by-step explanation:

$\displaystyle \frac{x^2 + y^2 - z^2}{2xy} = cos∠Z \\ \frac{x^2 - y^2 + z^2}{2xz} = cos∠Y \\ \frac{-x^2 + y^2 + z^2}{2yz} = cos∠X \\ \\ \frac{-8^2 + 14^2 + 21^2}{2[14][21]} = cos∠X → \frac{-64 + 196 + 441}{588} = cos∠X → 0,9744897959... = cos∠X \\ \\ 12,969468847...° = cos^{-1}\:0,9744897959... \\ \\ 13° ≈ 12,969468847...°$

As you can see, the inverse function MUST be used towards the end of your result, or elce you will throw it off!

I am joyous to assist you at any time.