Question

if sinθ=3/5 and θ terminates in the first quadrant, find the exact value of cos2θ

Answer 1

i'm gonna use x instead of theta...
since x is in the first quadrant, cosx=4/5... (use this is a 3-4-5 triangle)

so using the double angle formula:
cos2x = cos^2(x) - sin^2(x)
= (4/5)^2 - (3/5)^2

can you take it from here?

Answer 2

@viictor Do you still need help?

Answer 3

7/25?

Answer 4

sure

Answer 5

Do you up why -> cosx=4/5 ?

Answer 6

Do you know why?

Answer 7

its a 3 4 5

Answer 8

cos2x = cos^2(x) - sin^2(x)
= (4/5)^2 - (3/5)^2
So you okie here, right?

Answer 9

yes

Answer 10

So you're fine with your result :)

Answer 11

is it 7/25?

Answer 12

(16 - 9 )/ 25 = 7/ 25

Answer 13

so yes thanks

Answer 14

The key is knowing the trig, formula!

Answer 15

theyres to many

Answer 16

Yup. there's only one way to make yourself better is practice more, like I'm doing now :)

Answer 17

what about this one If sinθ=-1/4 and θ terminates in third quad., find the exact value of sin 2θ

Answer 18

Could you open the new post, pls!

Answer 19

i did

Answer 20

where?

Answer 21

Start a new post , new page!

Answer 22

http://openstudy.com/study#/updates/4fb9b010e4b05565342e9f3b