Respuesta :

Answer:

[tex]Side\ B = 6.0[/tex]

[tex]\alpha = 56.3[/tex]

[tex]\theta = 93.7[/tex]

Step-by-step explanation:

Given

Let the three sides be represented with A, B, C

Let the angles be represented with [tex]\alpha, \beta, \theta[/tex]

[See Attachment for Triangle]

[tex]A = 10cm[/tex]

[tex]C = 12cm[/tex]

[tex]\beta = 30[/tex]

What the question is to calculate the third length (Side B) and the other 2 angles ([tex]\alpha\ and\ \theta[/tex])

Solving for Side B;

When two angles of a triangle are known, the third side is calculated as thus;

[tex]B^2 = A^2 + C^2 - 2ABCos\beta[/tex]

Substitute: [tex]A = 10[/tex],  [tex]C =12[/tex]; [tex]\beta = 30[/tex]

[tex]B^2 = 10^2 + 12^2 - 2 * 10 * 12 *Cos30[/tex]

[tex]B^2 = 100 + 144 - 240*0.86602540378[/tex]

[tex]B^2 = 100 + 144 - 207.846096907[/tex]

[tex]B^2 = 36.153903093[/tex]

Take Square root of both sides

[tex]\sqrt{B^2} = \sqrt{36.153903093}[/tex]

[tex]B = \sqrt{36.153903093}[/tex]

[tex]B = 6.0128115797[/tex]

[tex]B = 6.0[/tex] (Approximated)

Calculating Angle [tex]\alpha[/tex]

[tex]A^2 = B^2 + C^2 - 2BCCos\alpha[/tex]

Substitute: [tex]A = 10[/tex],  [tex]C =12[/tex]; [tex]B = 6[/tex]

[tex]10^2 = 6^2 + 12^2 - 2 * 6 * 12 *Cos\alpha[/tex]

[tex]100 = 36 + 144 - 144 *Cos\alpha[/tex]

[tex]100 = 36 + 144 - 144 *Cos\alpha[/tex]

[tex]100 = 180 - 144 *Cos\alpha[/tex]

Subtract 180 from both sides

[tex]100 - 180 = 180 - 180 - 144 *Cos\alpha[/tex]

[tex]-80 = - 144 *Cos\alpha[/tex]

Divide both sides by -144

[tex]\frac{-80}{-144} = \frac{- 144 *Cos\alpha}{-144}[/tex]

[tex]\frac{-80}{-144} = Cos\alpha[/tex]

[tex]0.5555556 = Cos\alpha[/tex]

Take arccos of both sides

[tex]Cos^{-1}(0.5555556) = Cos^{-1}(Cos\alpha)[/tex]

[tex]Cos^{-1}(0.5555556) = \alpha[/tex]

[tex]56.25098078 = \alpha[/tex]

[tex]\alpha = 56.3[/tex] (Approximated)

Calculating [tex]\theta[/tex]

Sum of angles in a triangle = 180

Hence;

[tex]\alpha + \beta + \theta = 180[/tex]

[tex]30 + 56.3 + \theta = 180[/tex]

[tex]86.3 + \theta = 180[/tex]

Make [tex]\theta[/tex] the subject of formula

[tex]\theta = 180 - 86.3[/tex]

[tex]\theta = 93.7[/tex]

Ver imagen MrRoyal
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