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Lighthouse B is 9 miles west of lighthouse a a boat leaves a and sales 6 miles. At this time it is lighted from B. If the bearing of the boat from B is North 64° east how far from be is the boat?

Sagot :

Oladayoademosuidn

Answer:

12.61 miles

Step-by-step explanation:

The distance of lighthouse B from lighthouse A, the distance from lighthouse A to the boat and the distance of lighthouse B from the boat all form a triangle. Since lighthouse B is west of lighthouse A, and at a distance of 9 miles form lighthouse A, light house A is at a bearing of North 90° East of lighthouse B. The distance from lighthouse A to the boat is 6 miles, and the bearing of the boat from lighthouse B is North 64° East.

So, the angle between the distance from lighthouse B to the boat and lighthouse B to lighthouse A is 90° - 64° = 26°

Since we have two sides and an angle, we use the sine rule

a/sinA = b/sinB where a = 6, A = 26°, b = 9, B = unknown

So, sinB = bsinA/a

= 9sin26/6

= 3(0.4384)/2

= 1.3151/2

= 0.6576

B = sin⁻¹(0.6576)

= 41.11°

≅ 41.1°

We now find the third angle in the triangle, C(the angle facing the distance from lighthouse B to the boat) from

26° + 41.1° + C = 180° (sum of angles in a triangle)

67.1° + C = 180°

C = 180° - 67.1° = 112.9°

Using the sine rule again to find the third side, c(the distance from lighthouse B to the boat), we have

a/sinA = c/sinC

c = asinC/sinA

= 6sin112.9°/sin26°

= 6(0.9212)/0.4384

= 5.5271/0.4384

= 12.61 miles

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