Question

Can someone check my double angle calculations please? The equation is below

Answer 1

\[\sin 2\theta=\frac{ 4 }{ 5 }\]

Answer 2

my answer is \[\sin \theta=\frac{ 1 }{ \sqrt{5} }\]

Answer 3

aren't you meant to find theta?

Answer 4

well yes, but the question asked for Sin theta which is y/r :)

Answer 5

Looks good assuming that theta is in the is in the first quad. actually it could be positive or negative.

Answer 6

Use the half angle identity.

Answer 7

@Paynesdad i did, but i'm unsure of my work.

Answer 8

It is correct just include positive or negative.

Answer 9

Alright! thanks! :)

Answer 10

@Paynesdad Oh i forgot to mention why my answer was positive.. They told me that 2theta is between pi/2 (90degrees) and Pi (180 degrees) that excludes the negative answer correct?

Answer 11

Yes because no theta is between pi/4 and pi/2 and thus in the first quadrant. Good work.

Answer 12

Thank you :)

Answer 13

No problem.