Question

Sinx= 4/10 and secx<0 find exact value of cosx

Answer 1

have you learned about quadrant in trigonometry?

Answer 2

A little I know 2 and 3 are negative and 1 and 4 positive

Answer 3

Very perceptive. Now, in which quadrant does this angle lie?

Answer 4

Quadrant 4?

Answer 5

Why?

Answer 6

I don't know I was thinking either 1 or 4 because sin is positive

Answer 7

sin is not positive in quadrant 4

Answer 8

you're given that sin is positive.., and sec is negative..,
remember that sec = 1/cos ..,

Answer 9

So it would be quadrant 2?

Answer 10

yes... :)

Answer 11

So how would I go about finding cosx?

Answer 12

from the figure above.., can you label the side of right triangle given the value of sine x?

Answer 13

Opposite side would be 4 and the hypotenuse would be 10?

Answer 14

correct... :)

now.., what side you should know to find cosine x?

Answer 15

Use pytherogeam to get 2 sq root 21 and then put adj over hyp and divide then I ended up with sq root 21/5

Answer 16

do you mean