Posted by jeff on .
I am taking an online class, and cant understand why when I calculate ona ti84 plus an answer I get decimal answer and my teachers answer is sq root, is there something I am not doing on my calculator? How do I convert.
Example, teachers answer to the following was
sin 315deg = sin 45deg = sqrt2/2
I got a decimal answer.

algebra 2 
Reiny,
You should become familiar with two important special triangles
1. the 454590 rightangled triangle whose sides are in the ratio
1 : 1 : √2
2. the 306090 rightangled triangle whose sides are in the ratio of
1 : √3 : 2
The question to find sin 315° probably says to find it "exactly"
I do these in a 3step process
1. Where is the angle?
315 is in IV and in IV the sine is negative
2. How far from the xaxis ?
315° is 45° from the xaxis
The answer to this question will always be an angle between 0 and 90, it will be called the "angle in standard position, or ASP)
3. Rewrite the question in terms of the ASP
sin 315 = sin 45
From your special triangles
sin 45 = 1/√2 or √2/2 after rationalizing
so sin 315 = sin 45 = √2/2 
algebra 2 
greg,
In the matrix below, which element is a1,2?
1
4
7
2
5
8
3
6
9
A. 8 C. 6
B. 5 D. 2
Examination