Content Standards

Preparation for G.SRT.7 Explain and use the relationship between the sine and cosine of complementary angles.

Mathematical Practices

2 Reason abstractly and quantitatively.

3 Construct viable arguments and critique the reasoning of others.

You measured and classified angles.

• Identify and use special pairs of angles.

• Identify perpendicular lines.

• adjacent angles

• linear pair

• vertical angles

• complementary angles

• supplementary angles

• perpendicular

Identify Angle Pairs

A. ROADWAYS Name an angle pair that satisfies the condition two angles that form a linear pair.

A linear pair is a pair of adjacent angles that make a straight line. The sum of the angles is 180°.

Sample Answers: PIQ and QIS, PIT and TIS, QIU and UIT

Identify Angle Pairs

B. ROADWAYS Name an angle pair that satisfies the condition two acute vertical angles.

Sample Answers: PIU and RIS, PIQ and TIS, QIR and TIU

A. Name two adjacent angles whose sum is less than 90.

B. Name two acute vertical angles.

Angle Measure

ALGEBRA Find the measures of two supplementary angles if the measure of one angle is 6 less than five times the measure of the other angle.

Understand The problem relates the measures of two supplementary angles. You know that the sum of the measures of supplementary angles is 180.

Plan Draw two figures to represent the angles.

Angle Measure

6x – 6 = 180 Simplify.

6x = 186 Add 6 to each side.

x = 31 Divide each side by 6.

Solve

Angle Measure

Use the value of x to find each angle measure.

mA = x mB = 5x – 6

= 31 = 5(31) – 6 or 149

Answer: mA = 31, mB = 149

Check Add the angle measures to verify that the angles are supplementary.

mA + mB = 180

31 + 149 = 180

180 = 180

ALGEBRA Find the measures of two complementary angles if one angle measures six degrees less than five times the measure of the other.

• Practice Problems

• P. 50-51 1-3, 9, 15, 19, 21

Perpendicular Lines

ALGEBRA Find x and y so thatKO and HM are perpendicular.

Perpendicular Lines

90 = (3x + 6) + 9x Substitution

90 = 12x + 6 Combine like terms.

84 = 12x Subtract 6 from each side.

7 = x Divide each side by 12.

Perpendicular Lines

To find y, use mMJO.

mMJO = 3y + 6 Given

90 = 3y + 6 Substitution

84 = 3y Subtract 6 from each side.

28 = y Divide each side by 3.

Answer: x = 7 and y = 28

p. 49 Read 2 paragraphs above this diagram

Interpret Figures

A. Determine whether the following statement can be justified from the figure below. Explain.

mVYT = 90

Interpret Figures

B. Determine whether the following statement can be justified from the figure below. Explain.

TYW and TYU are supplementary.

Answer: Yes, they form a linear pair of angles.

Interpret Figures

C. Determine whether the following statement can be justified from the figure below. Explain.

VYW and TYS are adjacent angles.

Answer: No, they do not share a common side.

A. Determine whether the statement mXAY = 90 can be assumed from the figure.

A. yes

B. no

B. Determine whether the statement TAU is complementary to UAY can be assumed from the figure.

A. yes

B. no

• Class Assignment• p. 50 – 52 4 -6, 17, 25, 29, 31

• HW p. 51-52 8-16 even, 20, 22, 26,

Read 1-6 Take Notes

• Constructing Perpendiculars p. 55