A lighthouse beacon is 140m above sea level. The waters around it abound in rocks as far as 100m from the base of the lighthouse. an observer on the dect of a ship 7m above sea level finds that the angle of elevation of the beacon is 30 degrees. how many meters is the ship clear off from the rocks?

we can't use calculator, so we can only rely on circular function :((

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What does the second sentence mean? I don't get it. Sorry.

Answers

2014-03-25T12:41:36+08:00
If you could create a proper diagram of this question, you could actually answer this without using a calculator.

If the angle is 30 degrees, just remember the values of the unit circle with respect to angles in radians.

30 degrees is equivalent to π/6

sin(π/6)=1/2
cos(π/6)=(√3)/2
tanx=sinx/cosx

Hope that helps.

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