tailieunhanh - SAT Math Essentials for English_5

Tham khảo tài liệu 'sat math essentials for english_5', ngoại ngữ, anh ngữ phổ thông phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | GEOMETRY REVIEW Angles An angle is formed by two rays and an endpoint or line segments that meet at a point called the vertex. Naming Angles There are three ways to name an angle. 1. An angle can be named by the vertex when no other angles share the same vertex ZA. 2. An angle can be represented by a number or variable written across from the vertex Z1 and Z2. 3. When more than one angle has the same vertex three letters are used with the vertex always being the middle letter Z1 can be written as ZBAD or ZDAB and Z2 can be written as ZDAC or ZCAD. The Measure of an Angle The notation mZA is used when referring to the measure of an angle in this case angle A . For example if ZD measures 100 then mZD 100 . 99 GEOMETRY REVIEW Classifying Angles Angles are classified into four categories acute right obtuse and straight. An acute angle measures less than 90 . Acute Angle A right angle measures exactly 90 . A right angle is symbolized by a square at the vertex. Right Angle An obtuse angle measures more than 90 but less then 180 . Obtuse Angle A straight angle measures exactly 180 . A straight angle forms a line. Straight Angle 100 GEOMETRY REVIEW Which of the following must be true about the sum of mZA and mZB a. It is equal to 180 . b. It is less than 180 . c. It is greater than 180 . d. It is equal to 360 . e. It is greater than 360 . Answer c. Both ZA and ZB are obtuse so they are both greater than 90 . Therefore if 90 90 180 then the sum of mZA and mZB must be greater than 180 . Complementary Angles Two angles are complementary if the sum of their measures is 90 . Supplementary Angles Two angles are supplementary if the sum of their measures is 180 . .