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Quote:
If AB = BC, DA = AC, and angles DCB and ABC are right angles as shown above, then what is the value of xº?

Answer D:
<BAC=<BCA=45

<BCA+<ACD=90
<ACD= 45 =<ADC

<ACD + <ADC + <DAC = 180
<DAC =90

Please hit kudos if you liked the solution! Cheers :)
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Since triangle ABC is isoceles, angle A = angle C = 45
Since BCD is 90, then the remaining angle = 45
Since ADC is isoceles, x = 180-(45*2) = 90 D
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Bunuel

If AB = BC, DA = AC, and angles DCB and ABC are right angles as shown above, then what is the value of xº?

A. 30º
B. 45º
C. 60º
D. 90º
E. 105º





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Attachment:
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IMO D, Follow the attachment steps.

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Bunuel

If AB = BC, DA = AC, and angles DCB and ABC are right angles as shown above, then what is the value of xº?

A. 30º
B. 45º
C. 60º
D. 90º
E. 105º





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Attachment:
1.png

Clearly, <BAC = <BCA = 45 each
<BCA = <ACD = <ADC = 40 each
x + 90 = 180
x = 90 (D), IMO!
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Triangle ABC forms a isosceles right triangle since side AB and BC are equal. Hence Angle A=Angle C=(180-B)/2= (180-90)/2=45 degrees

Now in Triangle ADC, Angle C=90-45=45 degrees.
Since AD=AC Triangle ADC forms isosceles triangle with angles opposite to equal sides measuring 45 degrees each.
So angle x measures 180-(45+45)=90 degrees.

IMO option (d) is the correct answer.
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