Since Circular Measure has now made its way into the New Syllabus, E-Maths students now have to be careful to express your angle `θ` to **RADIAN** in your arc length and sector area formulae.

On top of that, A-Maths students must remember to do likewise whenever you see range of angles like 0 < `x` < 2`π` in any of your trigonometry questions!

radian mode is when calculating arc length and area of sector (when using s= r x θ for arc length and a= r^{2} x θ/2 for area of sector)

also for A Maths questions when range is given in terms of pi.

Degrees mode for everything else.

Am I right?

So in our case we have 3 *lower* points `A`, `B` and `E` (from the workings in comment #7) looking upwards towards a common point `D`.

However each of the points `A`, `B` and `E` has a *different* angle of elevation as their respective distances from `D` (or `C`) is different.

So to summarize once more the angles of elevations obtained from the workings in Comment#7:

∠ of elevation from `A` = 38.1°

∠ of elevation from `B` = 29.1°

∠ of elevation from `E` = 42°

One can safely assume that these angles are the max/min values since all other points between `A` & `E` & `B` would have angles that are < 42° and > 29.1°

Where would you rather sit if you want your neck to bend upwards the least?

Which is the worst spot where your neck needs to bend upwards the most?

P.S. Not sure if Miss Loi understood the 2nd part of your question, but if you know your *TOA CAH SOH* the angle can still be found if you know the distance from `AB` to `D` (the hypotenuse) - but this will of course depend on what's given in the question.

.l ]]>

Oh, and

**Happy Birthday Gal!**

And **Someone**, there's absolutely nothing to be embarrassed about. As the old adage goes: "It's better to have tried and pressed the calculator buttons wrongly then never tried at all"! 😉

**Someone:** Your error is in Part 2 (area of the Δ `ABC`) but your working's fine so it could be down to pushing the wrong buttons in your calculator.

As you can see, in a multi-part question, an error in an earlier part can easily snowball into errors in later part of the question (i.e. Part 5) so please tread with care!

Though it's probably not related to your case, Miss Loi would like to take this opportunity to remind all students to make sure your calculator is set to **DEGREE MODE** (vs RADIAN) to avoid a repeat of the tragedies that have been afflicting many students.

Do you know then, which kind of questions would require you to express your angles in RADIANS (e.g. `π`, `π`/2 etc.)?

And a nice touch for the *TOA CAH SOH* parts in your workings and for this question we can safely assume that the angles of elevation will never exceed 90°, else the screen will be on top and over everyone's head!

This is not an Omnimax theatre! LOL

]]>Oh and I find that someone who 捷足先登 made a mistake. ]]>