School : SMP N 3 Godean
Subject : Mathematics
Grade/Semester : VII/1
1. Pre-teaching (5 minutes)
a. Teachers give greetings to the students and led the students to pray.
b. The teacher reminds the material that has been presented at previous meetings that will be used in the comparison of the sides in a right triangle, namely about the Pythagorean theorem. Students write the formula of Pythagorean theorem.
c. Teachers motivate students by providing an overview of the benefits that will be gained after studying comparative material on the sides of a right triangle that is able to use it to solve problems of everyday. For example The Cyclone roller coaster at New York’s Coney Island is one of the most copied roller coasters in the world. Since it was built in 1927, seven copies of the coaster have been built. The first drop is 85 feet tall, and it descends at a 60° angle. The top speed is 60 miles per hour. You can use the Pythagorean Theorem to estimate the length of the first hill.
2. Main Activities (15 minutes)
a. The teacher distribute the student’s worksheet then the students do the activity 1 in their student’s worksheet while the teacher drew a equilateral triangle ABC with a CD as a altitude, and D is the central point of AB so length of AD = BD with BC i.e. cm.
b. The teacher asked the students to discuss their work with their friends to get the right answer. After all of the students finished then one of them explain his/her result.
c. Teachers inform the comparison of the sides in a right triangle (30o, 60o, 90o ) that obtained from the calculation of the length of the CD which was written on the board by students.
d. The students do the activity two while the teacher drew a isosceles right triangle ABC. Right on B with a length of AB = BC = x cm.
e. After all of the students finished then one of them explain his/her result. Thus acquired the long-side comparison on right triangle angle 45o, 45o, 90o
f. Teachers inform the results of comparison on right triangle angle 45o, 45o, 90o which obtained from the calculation of the length of the AC which was written on the board by students.
3. Closing (5 minutes)
a. The students make the summaries of the material by the direction from teacher.
b. The teacher gives individual assignments to the students.
c. The teacher encourages the students to study at home.
Learning Sources and Media
Sources : Dewi Nuharini dkk. 2008. Matematika 2 :Konsep dan Aplikasinya. Jakarta: Pusat Perbukuan, Departemen Pendidikan Nasional.
Media : student’s worksheet