# Angle A is in standard position with its terminal arm in quadrant III, the Trigonometry ratio sinA=-3/7 is given, how do you find the values of the other ratios?

##### 1 Answer

There are, broadly speaking, two approaches.

No pictures or thinking about pictures (or not much)

We are given:

This tells us that:

Now the fact that A has terminal side in Q III tells us the

Now that we have

**Method 2,** thinking about the definitions of the trigonometric ratios:

There are several possible approaches to this:

**2a:**

Think of

with

Now use

And the fact that we are in Q III, to get

**2b**

for points on the terminal side

and

We can choose one of these points (the unit circle approaches chooses

Let's make

In Q III, we must have

Now: