Students’ Mathematical Communication Ability in Solving Trigonometric Problems

Mathematical communication ability is a person’s ability to convey mathematical ideas orally or in writing which are presented in the form of graphs, tables, diagrams, symbols, or mathematical models. The purpose of this study is to determine and describe the level of mathematical communication ability of students. This type of research is a qualitative descriptive study. The sampling technique was using a purposive sampling technique. The results showed that the percentage of students’ mathematical communication ability in the text writing indicator, 38% of students were in the poor category, 50% of students were in the moderate category, 11% of students were in a good category, and 4% of students were in the very good category. On the drawing indicator, 7% of students were in the poor category, 57% of students were in a low category, and 36% of students were in the moderate category. 14% of students were in the poor category, 50% of students were in a low category, 18% of students were in the moderate category, 11% of students were in a good category, and 7% of students were in the very good category.


Research Methods
This type of research is a qualitative descriptive study. Research using this method aims to describe the conditions that occur during the research. The sampling technique in this study is by using purposive sampling. The subjects of this study were 28 students of class XI IPA. The instrument used was a twoitem mathematical communication skill test item with three indicators of mathematical communication ability. The flow diagram in this study as follows in figure 1:

Figure 1. Research Flow Diagram
The indicators of mathematical communication ability in this study can be seen in Table 1 Table  2 below. According to Sriwahyuni [28], the percentage of students' mathematical communication ability can be known by the following formula: Information: P: Percentage in each category X i : Student who meet level i on each indicator; = 0,1,2,3,4 Y: Many students took the test

Results and Discussion
The results of the students' mathematical communication ability test can be seen in Table 3 below: Table 3.

Results of the Mathematical Communication Ability Test
Indicator to- Ability  Total  Students  0  1  2  3  4  1  0  10  14  3  1  28  2  2  16  10  0  0  28  3  4  14  5  3  2  28 The percentage of categories of students' mathematical communication ability can be seen in Table  4 below: In the second and third indicators, there were two and four students with mathematical communication ability level 0, respectively. The students' inability to answer questions can be influenced by several factors, such as a lack of understanding of the concept of trigonometric material or a lack of understanding of the questions given.

Students with level 1 mathematical communication ability
In the first indicator, students with level 1 mathematical communication ability are 10 students. One of the students' answers can be seen in Figure 2 below: Based on Figure 2, students have been able to write several steps in their language but they are incorrect and difficult to understand. This can be seen from 1 where students draw an isosceles triangle, even though students should draw a right triangle. Furthermore, in 2 students are known to be able to understand that before looking for cos and tan they must first find the side using the Pythagoras formula, but students are still wrong in writing formulas and doing calculations. In 3 , students did not write the formula to look for cos and tan , which were still wrong in entering the known numbers in the formula tan .
In the second indicator, students with level 1 mathematical communication ability are 16 students. One of the students' answers can be seen in Figure 3 below :  Figure 3, students have been able to paint pictures but they are incorrect and incomplete. This can be seen from 4 which shows that students do not write down the two known angles and do not have an idea to find the other angles so that students cannot know that the location of the three children will form a right triangle.
In the third indicator, students with level 1 mathematical communication ability are 14 students. One of the students' answers can be seen in Figure 4 below: Based on Figure 4, students are only able to write formulas and cannot make mathematical models. This can be seen from 5 where students are not able to make mathematical models correctly to solve problems based on the formula that has been written. Furthermore, on 6 students did not write in full how these results were obtained. This shows that students are not clear and complete in solving problems.

3.1.3
Students with level 2 mathematical communication ability In the first indicator, students with level 2 mathematical communication abilities are 14 students. One of the students' answers can be seen in Figure 5 below: Based on Figure 5, students have written several steps but only partially correct and the answers are still incomplete and clear. This can be seen in 7 where students do not write that students will sketch pictures as a first step to make it easier to solve problems. Furthermore, in 8 students did not write down how to find the side length. This shows that students do not write down all the steps clearly and systematically.
In the second indicator, students with level 2 mathematical communication ability are 10 students. One of the students' answers can be seen in Figure 6 below: Based on Figure 6, students have painted a picture by providing information but it is still wrong. Students can imagine that the sketch will form a right triangle after knowing the size of the other angles, but are still wrong in positioning the image so that it matches the size of the known angle. This is indicated by 9 where students at right angles write down the angles of 60 o , even though the right angles should be 90 o .
In the third indicator, students with level 2 mathematical communication ability are 5 students. One of the students' answers can be seen in Figure 7 below:  Figure 7, students can write formulas and create mathematical models to solve problems but are still wrong in doing calculations. In 10 , students are not consistent in writing symbols that match their mathematical models. In 11 , students make calculation errors in finding solutions to problems.

Students with level 3 mathematical communication ability
In the first indicator, students with level 3 mathematical communication ability are 3 students. One of the students' answers can be seen in Figure 8 below: Based on Figure 8, students have written all the steps but there is a little language that is unclear and wrong. This can be seen in 12 where students do not provide information that the Pythagoras formula  In the second indicator, there are no students who have level 3 mathematical communication ability.
In the third indicator, students with level 3 mathematical communication ability are 3 students. One of the students' answers can be seen in Figure 9 below: Based on Figure 9, students can write formulas and create mathematical models to solve problems correctly but not completely. In 13 , students do not provide information and units for the calculation results so that students are not complete in solving problems.

Students with level 4 mathematical communication ability
In the first indicator, students with level 4 mathematical communication ability are 1 student. One of the students' answers can be seen in Figure 10: Based on Figure 10, students have written all steps using their language correctly, clearly, and completely.
In the second indicator, there are no students who have level 4 mathematical communication ability. In the third indicator, there are 2 students with mathematical communication ability level 4. One of the students' answers can be seen in Figure 11: