Core Connections Integrated II, 2015
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Core Connections Integrated II, 2015 View details
1. Section 7.1
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Exercise 16 Page 378

Practice makes perfect
a Examining the diagram, we see two triangles inside of △ ABC. Notice that two of these triangle's angles form a linear pair, which have been marked below.
The angles of a linear pair are supplementary, and because one angle is a right angle the second angle must be right as well.

m∠ θ+90^(∘)=180^(∘) ⇔ m∠ θ =90^(∘) Also, notice that these right triangles share their vertical side. Therefore, this side is congruent as well according to the Reflexive Property of Congruence.

Since two pairs of sides and the included angle are congruent, we can claim that the triangles are congruent by the SAS (Side-Angle-Side) Congruence Theorem. Now we can identify corresponding sides.

To find the value of x we can use the Pythagorean Theorem.
a^2+b^2=c^2
8^2+x^2=10^2
Solve for x
64+x^2=100
x^2=36
x=± 6

x > 0

x=6
b In the diagram we see one pair of congruent angles and can also identify a pair of Alternate Interior Angles.

Since AB∥DC, by the Alternate Interior Angles Theorem we can claim that these angles are congruent. The triangles have two pairs of congruent angles, which means we know by the AA (Angle-Angle) Similarity Theorem that they are similar.

To claim congruence we also must show that at least one pair of corresponding sides is congruent. Notice that both triangles share BD as a side. Since this side is between the same two pairs of congruent angles, it shows two corresponding sides in our triangles.

Now we can claim congruence by the ASA (Angle-Side-Angle) Congruence Theorem. Note that AD and BC are corresponding sides, which means x=10.

c Examining the diagram, we see that △ ADC and △ CBD are both right triangles with one pair of congruent legs. They also share their hypotenuse, which means it is also congruent according to the Reflexive Property of Congruence.

Now we can claim congruence by the HL (Hypotenuse-Leg) Congruence Theorem, where ∠ CAB and ∠ ACD are corresponding angles.

Finally, to calculate x we can use the tangent ratio.
tan(θ) =Opposite/Adjacent
tan(35^(∘)) =11/x
Solve for x
xtan(35^(∘)) =11
x =11/tan(35^(∘))
x =15.70962...
x ≈ 15.71
d Examining the diagrams, we see that the triangles have two pairs of congruent angles.

With this information we can claim similarity by the AA Similarity Theorem. However, we do not have enough information about the side lengths. Therefore we do not have enough information to claim congruence, which means we cannot find x.