Question

Use the Pythagorean Identities to solve the following:
1) Find sinθ, if cosθ= 3/5 and θ terminates in Quadrant I
2) Find cosθ⁡ if sinθ⁡ = 1/(3 ) and θ terminates in Quadrant II
3) Find secθ⁡ if tanθ⁡ = 8/(15 ) and θ terminates in Quadrant III

Answer 1

Using the Pythagorean identity,

cos2

θ

+

sin

2

θ

=

1

So.

9

25

+

sin

2

θ

=

1

sin

2

θ

=

1

−

9

25

=

16

25

∴

sin

θ

=

√

16

25

=±

4/5