Posted by **jeff** on Sunday, May 16, 2010 at 9:14am.

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**, Sunday, May 16, 2010 at 10:51am
You should become familiar with two important special triangles

1. the 45-45-90 right-angled triangle whose sides are in the ratio

1 : 1 : √2

2. the 30-60-90 right-angled 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 3-step process

1. Where is the angle?

315 is in IV and in IV the sine is negative

2. How far from the x-axis ?

315° is 45° from the x-axis

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**, Sunday, May 16, 2010 at 11:52am
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

## Answer this Question

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