Controversial Question - Module 2, Geometry - Question 6 - Come and decide

[krzysiek]

Hey guys,

I have seen a few people around here posting solutions for Question 6 of Module 2, Geometry, as answer A.

The question readers, "The angle of depression of D from A is closest to";

This means, you find the angle of A, as that is the angle of depression, down to D. Many give the answer A, which is 21.5, but that is the angle of elevation of A from D. We are finding D from A, and it also says "angle of depression" hinting that it is the angle near A.

The correct answer, I think*, is D - 68.5 degrees.

Prove me wrong if you wish, but I hope you don't, as I want to keep my score

[rustic_metal]

I believe module two is wrong.

Question 6 you guys have A as the answer, which corresponds to 21.5 degrees.

It asks, the angle of depression of D FROM A. So, you calculate the angle of A. Also, the hint is in "depression". Many of you seem to have found angle D, which is elevation.

Either way, just my opinion and nothing official..

Answer should be 68.5 I think.

(Image removed from quote.)

The angle of Depression from D from A is equivalent to the angle of Elevation from D to A: The angle RDA

[dior1]

I put that answer down too, only because i realised it was a Z angle and therefor it was 21.something..

[murplp]

angle of depression is the same as angle of elevation is it not?

[krzysiek]

When I calculate angles RDA and RAD I get two different values... they do not seem to be the same. You also say that it angle of elevation from D to A is equivalent to the angle of D from A. If both angles are equal, and you guys chose 21.5 as the right answer, then 21.5 x 2 = 43 degrees. The other angle is 90 degrees (right angle) 90 + 43 = 133. But it must add up to 180 in a tri-angle, so the angles RDA and RAD can not be equal. Besides, the side lengths are different.

Please help me, as I am wondering which one is the right answer now. Be descriptive.

[magnum]

This is another way to do it:

1. Angle of depression is always from the horizontal

2. Therefore, find angle RAD (which is 68.5) and then subtract this from 90:

90 - 68.5 = 21.5 degrees

[krzysiek]

Aha, from the horizontal. That got me :p

Cheers for that, down to 38/40. Fuck my life.

I hope I can still get 40+ raw for this.

[mtlz]

i can't remember that question
but 21.5 seems familliar that is definitely wrong ugh?

[magnum]

i can't remember that question
but 21.5 seems familliar that is definitely wrong ugh?

21.5 is right lol 

[mtlz]

omg you guys are making me so happy right now
just have one more question
if it's right then i'm really  happy with my paper then wow

[lankygator]

do u need to get full marks for a fifty, what is the lowest possible to still get a fifty

[krzysiek]

I think if you lose a mark, there goes a fifty

[lankygator]

well thats just S***,  does anyone have the workings to question 9 geometry???

[rustic_metal]

well thats just S***,  does anyone have the workings to question 9 geometry???

To find the distance from the pole to the wall (y), I equated herron's formula with 1/2bh:

s = (6+4+5)/2 = 7.5

A= root(s(s-6)(s-4)(s-5)) = 1/2 x 6 x y

y = root(s(s-6)(s-4)(s-5))/3 = 3.307m

Then we want the height up the wall when the pole is leaning on it:

x^2 + y^2 = 4^2
.: x = root(4^2 - y^2) = 2.25m ~ 2.3m

.: C

[Ilovemathsmeth]

Angle of elevation is equal to angle of depression according to alternate angle property. Thus it is correct to say 21.5