Calling all maths people!


Look on that site.

Using only elementary geometry determine the value of the angle marked “x.”

For the purpose of this let’s call the vertex of the lowermost triangle point “f.”

So there are a few easy bits. Angle AFB is 50 degrees because the angle sum of any triangle is 180, subtract the sum of seventy and sixty, and then Angle DFE is also 50 degrees because it’s vertically opposite to AFB.

Thus it stands that angle X is equal to 180 - (50 + angle FDE) but you still need FDE.

…I cannot find Angle FDE. >.>

I’ve tried everything. I’ve used every triangle visible and every geometric convention or technique or whatever to no avail. FDE eludes me.

We also know that AEB is 30 (angle sum again) and that angle EDB can give us x by subtracting 30 from it but again I’m screwed over the lack of a value for FDE- or EDB in this case. Whichever, same angle.

I know that ADB is 40 (angle sum again) and ACB is 20 (angle sum) and every other frickin’ value but FDE/EDB/CDB.

Mathematics people, halp! This is something I enjoy doing in my free time but this one drives me up a wall.

I can’t solve it. ;W; Halp plox. I am a pleb. Enlighten me.


Lol let me try this.


x = 40º

I would explain, but i suck at it.


Kay, I’ll run that through and check.


It doesn’t work.


Thats wierd, acording to my maths, the triangle below the DEF ( F being that point between D and B ) should be 70 + 60 -180 that gives 50, which then means the angle DFE is 50º, if you notice, EDB is a 90º angle, so you do 50+90-180 which should end up with X = 40º

DEF = 50º and
EDF = 90º


Reads through thread.


No, it is not. Can’t assume that unless it states so, and it doesn’t. :stuck_out_tongue:


Can’t be 80 nor 100, has to be 90 :stuck_out_tongue:


How so? It doesn’t give you any sort of value for that angle.


The way i learn maths is way different on my side, i will try another solution.

( ignore me below here i need to save my calculations. )

AEB = 30º

ADB = 30º as well.

OHH, if AEB = 30º, then DBE ( which equals 20º as shown ), that means 30+20-180 which equals 130º, meaning EFB = 130º

Considering that DFE + EFB MUST give 180º ( straight line is always 180 or 360, in this case its obviously 180 ) that means since EFB is 130º that, EFD is 50º

Good, good, im getting closer.


Ah, that explains it. :slight_smile: The way this question is made though takes Australian rulesets in mind by which you can only know the value of any given angle/side/whatever by proving it or having it presented to you.


Ok, i got closer, the angle EFD is 50º ( thats the one inside the triangle of our mysterious X ).


Yes, I gave that value in the OP. :stuck_out_tongue:


Don’t judge me miss, i am doing my very best xD

Oh please don’t tell me its what i think it is…

Nope nvm, false alarm.


Math is the worst.


Lol nah, no judgement here, I suuuuuuuuuuuuuuuuuuck at math. :stuck_out_tongue: As evidenced by this thread.

Just asking for help because I’m at a dead end here. :confused:


Neeeeeeeeuuuuuu. Why? :stuck_out_tongue:


Because, it is.


;W; So mean to maths.