Deduce questions (2 Viewers)

[pt1]

Hey I was wondering if there is any sort of method you would apply to a 'deduce' question such as those found in the later questions (9&10). Some I get but others I dont know where to start. Any tips?

 

[Carrotsticks]

You start from the previous part (or the part specified), then work out the final result from there.

There generally is no 'method', but look for clues regarding what you should do. Give us a sample question and we'll show you what we can.

 

[pt1]

Part IV, I looked at the solutions and they pulled a line outta nowhere which didnt make sense D:

 

[Carrotsticks]

So what goes in my mind, when I see this question, is this....

Okay cool part (iii) has cos theta, now to do par- WHAT where did the cos theta go!? Part (iv) has an inequality.... and the cos theta is gone..... The only thing I can think of that has an inequality, and cos theta in the same expression, is -1 < cos theta < 1, so perhaps I'll give that a go.

And the answer comes out immediately by substituting in the fact that cos theta > -1

 

[Sy123]

An alternate method is to understand that what we can grasp from this inequality is that the MAXIMUM y-value that y can take is 3a.

So lets use our expression from part iii:

 

[pt1]

Thanks!. On a side note are these trig inequalities part of the 2U course? I haven't seen them around before

 

[cutemouse]

are these trig inequalities part of the 2U course?

Yes they are. They're basically the range of the sin and cos functions.