2013 HSC - Trig Error??? (1 Viewer)

[swagmeister]

Heyo,

2013 HSC #4:


Let's call theta X

sin(X) = 81/135
∴ X = sin^-1 (81/135)
∴ X = 41^o

even trying cosine...

cos(X) = 108/135
X = cos^-1 (108/135)
X = 41^o

So this is not any of the options for the multiple choice........ the closest is 37^o, and that is what the marking guidelines say is correct, but am I missing something?

 

[VBN2470]

I get 37^o (36^o52' to be accurate) using my calculator, so I don't know if it's your calculator causing problems.

 

[BLIT2014]

Heyo,

2013 HSC #4:
View attachment 32074

Let's call theta X

sin(X) = 81/135
∴ X = sin^-1 (81/135)
∴ X = 41^o

even trying cosine...

cos(X) = 108/135
X = cos^-1 (108/135)
X = 41^o

So this is not any of the options for the multiple choice........ the closest is 37^o, and that is what the marking guidelines say is correct, but am I missing something?

Maybe try resetting your calculator...

θ=tan^-1 (81/108)
=36'52
=37

 

[Ambility]

Your working out is right, but is definitely equal to .

 

[swagmeister]

All good guys my calculator was in some weird mode, chucked it in degrees then got the right answer. At least I learnt this now rather than trials or HSC!

 

[BLIT2014]

All good guys my calculator was in some weird mode, chucked it in degrees then got the right answer. At least I learnt this now rather than trials or HSC!

Mine was in radians initially too!