can i please get some help? :)

[sam0001]

hey guys, how do you do this question?

[Stick]

Oh no, they've confused you with all that unnecessary information! It's as simple as sin(50)=14/AC.

[sam0001]

howww???

[Stick]

I'm not sure how to explain it to you, because it's sorta obvious... That question only involves the triangle ABC, it's right angled and they've given you an angle and a side length. The only way I can possibly explain your confusion is if you think the triangle isn't right-angled. The question says AB is at right angles with BD and then says that the triangle BCD is flat on the ground. Hence, AB is also perpendicular to BC.

[BubbleWrapMan]

That's not necessarily true though.

[Stick]

Of course it is, the question says the ground is horizontal... Look, if you're not getting it, try modelling the shape using some pens and pencils. You'll see it then.

[BubbleWrapMan]

The right hand edge of my laptop screen is perpendicular to the bottom edge, but it's not perpendicular to the surface on which my laptop is sitting.

[sam0001]

oh i was visualising the image in a completely different way to the way i should have. thanks!

[Stick]

The right hand edge of my laptop screen is perpendicular to the bottom edge, but it's not perpendicular to the surface on which my laptop is sitting.

I don't understand that. In this case BD and BC are on the same, level surface.

Sam, let me know if that gives you the right answer.

[sam0001]

yep, thanks!

do you think vcaa will be a bit more explicit though? i had no idea what they were talking about in this question.

[BubbleWrapMan]

AB can be perpendicular to BD without being perpendicular to the ground, is what I'm saying

And yes, they'd have easier questions than this

[Stick]

But BCD is the ground. Try to avoid over-thinking these sorts of problems, because they're not designed to be too difficult (especially for a part a question). If ABC was not right angled, then there would not be enough information to find AC.

[BubbleWrapMan]

It says it's perpendicular to BD, not BDC. They probably meant for it to be right-angled anyway but they didn't make it clear. VCAA would, though, so who cares I guess.

[Stick]

I still don't really understand your point of view, but VCAA would certainly make sure this is clear. Remember, a lot of trial exam papers try to test your spatial reasoning by forcing you to have to 'see' something in a given diagram. VCAA is trying to test your ability to use the mathematics in their course and hence don't try to trick students in that sort of way.

[Daenerys Targaryen]

AB can be perpendicular to BD without being perpendicular to the ground, is what I'm saying

And yes, they'd have easier questions than this

i see where you're coming from, but again that 'horizontal' is enough to assume the floor is flat and thus perpendicular to BC too