Question

An angle, theta, is in standard position and its terminal side passes through the point (2,-1). Find the EXACT value of sin theta.

Answer 1

Answer:

sinѲ = -1/√5 or -√5/5

Step-by-step explanation:

On the Cartesian plane, we have radius (r) and angle (Ѳ) theta.

On the Cartesian plane we also have x, y where:

x = r cosѲ .......Equation 1

and y = r sinѲ ........Equation 2

r = √x² + y²

In the question we are given points (2,-1)

Where x = 2 , y = -1

We would solve for r by substituting 2 for x and -1 for y

r = √ 2² + -1²

r = √ 4 + 1

r = √5

In the question, we were asked to find what sin theta (Ѳ) is. Hence, we would be substituting √5 for r in Equation 2

y = r sinѲ

Where y = -1 and r = √5

-1 = √5 sinѲ

Divide both sides by √5

sinѲ = -1/√5

We can also represent sin Ѳ in a proper form, by multiplying both top and bottom by √5

sinѲ = -√5/5

Therefore, sinѲ = -1/√5 of -√5/5