Deltamath finding angles | Mathematics | Page 1

latent wharf Oct 13, 2025, 10:46 PM

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I need to find the value of DEC, I’m really confused

copper patioBOT Oct 13, 2025, 10:46 PM

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bronze vine Oct 13, 2025, 10:50 PM

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Can you find an expression for DEC in terms of other angles?

latent wharf Oct 13, 2025, 10:52 PM

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Angle DEC + Angle CEB + Angle DEA= 180

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Wait sorry

bronze vine Oct 13, 2025, 10:52 PM

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You're right

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What is CEB?

latent wharf Oct 13, 2025, 10:52 PM

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33?

bronze vine Oct 13, 2025, 10:52 PM

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Why?

latent wharf Oct 13, 2025, 10:54 PM

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Becuase it’s equal to the bisected angle of c, which c is 66, so half of 66 is 33. Because CD and BA are parallel, their alternate interior angles are congruent?

bronze vine Oct 13, 2025, 10:54 PM

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Yup

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That sounds right

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Then what's DEA?

latent wharf Oct 13, 2025, 10:55 PM

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Also 33?

bronze vine Oct 13, 2025, 10:57 PM

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why?

latent wharf Oct 13, 2025, 10:58 PM

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Angle D is 66 because of alternate interior angles, and it’s bisected, so 66/2, 33?

bronze vine Oct 13, 2025, 10:58 PM

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Why is D 66?

cloud marten Oct 13, 2025, 10:59 PM

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Angle D =180⁰-66° because it's a pararelogram

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D=180⁰-A

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=114⁰

bronze vine Oct 13, 2025, 11:00 PM

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cloud marten Angle D =180⁰-66° because it's a pararelogram

the point isn't to just say the right answer, the point of helping is to get ppl to understand

latent wharf Oct 13, 2025, 11:00 PM

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cloud marten Angle D =180⁰-66° because it's a pararelogram

So each angle on each side on the same segment equals 180?

cloud marten Oct 13, 2025, 11:00 PM

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latent wharf So each angle on each side on the same segment equals 180?

Two angles on the same side equal to 180⁰

bronze vine Oct 13, 2025, 11:01 PM

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yeah

latent wharf Oct 13, 2025, 11:02 PM

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So 180-60=120, 120/2, so 60 is the value of CDE, therefore the value of DEA

cloud marten Oct 13, 2025, 11:02 PM

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See here, A isn't 60⁰, it's 66⁰

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If you change the numbers, yes, you are correct

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CDE= (180⁰-A):2, Because DE is a bisector

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180⁰-66=114⁰, 114⁰:2=57⁰

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Ok, so now, what do we have left?

latent wharf Oct 13, 2025, 11:05 PM

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I just realized I changed the numbers, so 180-66=114, divide that by 2 to find CDE, one part of the bisected angle

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So 57

latent wharf Oct 13, 2025, 11:05 PM

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cloud marten Ok, so now, what do we have left?

CED

cloud marten Oct 13, 2025, 11:05 PM

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To find out angle CED

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Yes

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Do you know how we do that

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?

latent wharf Oct 13, 2025, 11:06 PM

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latent wharf Angle DEC + Angle CEB + Angle DEA= 180

So we go back to this equation and substitute?

cloud marten Oct 13, 2025, 11:06 PM

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latent wharf So we go back to this equation and substitute?

Yes

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Correct

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From that formula, we can say that DEC=180⁰-DCE-CDE

latent wharf Oct 13, 2025, 11:07 PM

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Is it 90?

cloud marten Oct 13, 2025, 11:07 PM

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One sec

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180⁰-57-33=90, yes

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You have solved it :D

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The most important rule of this was that in a pararelogram, two angles of the same side equal 180⁰

#Deltamath finding angles