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Stuck on a 3D trig question!

RuWill2001

Hi,

Can someone please help with this question? I have got part A correct, but B and C are wrong.

The answers are below:

A: 11.5
B: 20.4°
C: 22.9°

Thanks!

Reply 1

Mr M

Study Forum Helper

Original post by RuWill2001

...

Could you rotate your picture please?

Reply 2

Mr M

Study Forum Helper

Original post by RuWill2001

Here, sorry, I didn't even realise! http://prntscr.com/dsn2zb

I've only glanced at it but M is in the wrong place on your diagram. M is the midpoint of AD.

Reply 3

RuWill2001

Original post by Mr M

I've only glanced at it but M is in the wrong place on your diagram. M is the midpoint of AD.

Ahh, thanks! I will try it now, thx!

Reply 4

HS2030

sorry. I'm usually good at this stuff but i don't get the question. :frown:

it would be a help if theimage was rotated

Reply 5

Mr M

Study Forum Helper

Original post by HS2030

sorry. I'm usually good at this stuff but i don't get the question. :frown:

it would be a help if theimage was rotated

There's a rotated version in post 2.

Reply 6

CraigBackner

for question b i got the same answer as you so im not sure what i did wrong

but for c, firstly m is the midpoint of ad not dc
to work out the angle first we have to work out the length of at least two sides of the triangle agc
so we have one given lenghth, gc which is 4cm, but we need to we need to work out the length of cm
the triangle cmd makes a right angle which we can use to work out cm

once youve worked that you you can use trigonmetry to work out the angle cmg