Math Is Fun Forum

tristan1

Member

Registered: 2005-11-19

Posts: 6

Trigonometry help!

Rubbish drawings I know but I really need help with these 4. CHeers!

Last edited by tristan1 (2006-01-16 06:34:10)

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Trigonometry help!

Top-left
Look at what you're given. You have the opposite side and you want to find the hypotenuse.
That means that you need to use sinθ = opp/hyp

Rearranging: hyp = opp/sinθ = 32/sin 56° = 38.60m (nearest cm)

Top-Right
Same again. Look at what you're given. You have the adjacent side this time and you still want to find the hypotenuse. So, you need to use cosθ = adj/hyp

Rearranging: hyp = adj/cosθ = 5.2/cos 23° = 5.65m (nearest cm)

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Try to do the bottom two on your own. They're exactly the same as the top two, just with different lengths and angles.

For future reference, you may also need tanθ = opp/adj, but you don't need that here.

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Why did the vector cross the road?
It wanted to be normal.

tristan1

Member

Registered: 2005-11-19

Posts: 6

Re: Trigonometry help!

Can anyone check or correct these answers I have please:

Bottom left: 171.334m
Bottom Right: 45.583m

irspow

Member

Registered: 2005-11-24

Posts: 1,055

Re: Trigonometry help!

I can't really read the numbers you had there but if;

171.334sin71° = what you wrote at the bottom,  you are correct! (162m)

45.583cos71° = what you wrote at the bottom, you are correct! (14.8m)

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I am at an age where I have forgotten more than I remember, but I still pretend to know it all.