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#1 2013-11-25 00:40:37

ninjaman
Member
Registered: 2013-10-15
Posts: 43

trig problem

hello
i have a problem that im stuck on, the question is this

from a ship at sea, the angles of elevation of the top and bottom of a vertical lighthouse standing on the edge of a vertical cliff are 31degrees, and 26 degrees respectively. if the light house is 25m high, how high is the cliff?

so far i have h+25/tan31 = h/tan26

rearrange to, (h+25)tan26 = h tan31

im lost after this

any help would be appreciated.

thanks
simon:)

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#2 2013-11-25 01:18:35

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,531

Re: trig problem

hi Simon,

You've done the correct thing so far and I got this, too.  smile

So multiply the bracket:

Move the h terms together:

Factorise the h:

And divide by the bracket ........

Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#3 2013-11-25 10:26:55

ninjaman
Member
Registered: 2013-10-15
Posts: 43

Re: trig problem

hello bob

thanks for the help!

I divided by the brackets? (I think), meaning I did what was in the brackets first

(tan31-tan26) = 0.1131280305 * h = 25 tan 26

then, divided the first half by 0.1131280305 to move it over and under to get

h = 25 tan 26
      0.1131280305 = 107.78332


is this correct, I have a feeling you meant something else by divide by the brackets and now im way off.

cheers
all the best
simon smile

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#4 2013-11-25 11:28:14

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,531

Re: trig problem

hello Simon,

That's spot on; well done!  smile

Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#5 2013-11-26 04:56:52

ninjaman
Member
Registered: 2013-10-15
Posts: 43

Re: trig problem

that's great!

thanks for your help bob!

all the best

simon:)

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