Can you solve for this angle, only using basic geometry, so no trigonometry?

Can you solve for this angle, only using basic geometry, so no trigonometry?
#maths
#mathematics
#math
#mathpuzzles #geometry
"Correction: 00:09 The two blue single line hash marks indicate the two lines are of same length. They should have been drawn orthgonal to side of the triangle."

[@hexcodeff6624]

The thumbnail is misleading because the markings for the sides being the same is basically invisible

[@MindMathEnigmas]

I've put in a new thumbnail

[@user-fx8hx9co1e]

30 degree

[@AjaySivaram-by8vl]

= Shift of all the best for the text of the day of people make it at what appears to do in evening

[@safewayz]

how could you tell the triangles are congruent?

[@MindMathEnigmas]

As stated in the video, it's Side-Angle-Side. Short sides equal (given in question), long sides equal, angle in between are both 20 degrees. You may want to read up on the 5 congruent triangle conditions:
SSS (Side-Side-Side)
SAS (Side-Angle-Side)
ASA (Angle-Side-Angle)
AAS (Angle-Angle-Side)
RHS (Right angle-Hypotenuse-Side).

[@get-the-joke]

@@MindMathEnigmas You didn't make clear that the lines with the blue dash have equal length.

[@MindMathEnigmas]

@get-the-joke You can read about meaning of hash mark here: en.wikipedia.org/wiki/Hatch_mark or mathbitsnotebook.com/Geometry/BasicTerms/BTnotation2.html

[@get-the-joke]

@@MindMathEnigmas At least make the hatch marks orthogonal to the sides as they usually are, better also mention their meaning to avoid confusion.

[@wilfriedsteinbach8700]

@@get-the-jokebruh

[@mustafaoguzmizrak8792]

Draw a regular nonagon. It is so easy to see the result.

[@JobBouwman]

Exactly my thought. And then expand the marked length at the right side into an equilateral triangle pointing downwards.
60'/2 = 30'

[@hohoy9563]

Oh, I found it 20. I think you should entitle the corners I dont know how to explain how I found 20

[@SonicLover47]

It’s 30

[@archangecamilien1879]

Should be easy, call the angle alpha, etc, the supplementary one would be 180-alpha, and use the fact that the sum of the angles in each triangle is 180, I'm guessing that should yield something for alpha...

[@edgardogiudice5135]

You 're so wrong.🙄