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I need help.ASAP.thanks

I need help.ASAP.thanks-example-1
User Arjuna
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1 Answer

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Both angles ABO and ADO are right angles because ABP and ADQ are tangent to circle O. The interior angles of a quadrilateral add up to 360 degrees, so the measure of angle BOD (and measure of minor arc BD, denoted
\widehat{BD}) is


y+m\angle BOD+90^\circ+90^\circ=360^\circ\implies m\angle BOD=180^\circ-y

This also means the measure of the central angle BOD that subtends major arc BCD (also the measure of the major arc BCD is)


m\widehat{BCD}=360^\circ-(180^\circ-y)=180^\circ+y

The inscribed angle theorem says that the measure of angle BOD is twice the measure of angle BCD, so


m\angle BCD=90^\circ-\frac y2

The interior angles of quadrilateral BCDO have sum


\underbrace{90^\circ-2x}_(m\angle CBO)+\underbrace{180^\circ+y}_{m\widehat{BCD}}+\underbrace{x}_(m\angle CDO)+\underbrace{90^\circ-\frac y2}_(m\angle BCD)=360^\circ

Simplifying this equation will give you
y=2x.

User Danny Gloudemans
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