Question

1.use a calculator to evaluate the expression
cos31deg*cos149-sin31deg*sin149
A. -0.4695
B. -1
C. 0
D. -0.8829
i got B. is that correct?
2.Find the exact trigonometric function value.
csc(-300deg)
A. sqrt2
B. 2sqrt3/3
C. -sqrt3/3
D. -2
i don't know about this one..i can only guess...pleaase help!!!

Answer 1

can someone please help

Answer 2

cos 31 cos (180-31) -sin 31 sin(180-31)
= -cos^2 31 -sin^2 31
= cos 62
=.4695

Answer 3

csc (-300) - csc 60 = 1/sin 60 = 2/sqrt 3 = 2 sqrt 3 /3

Answer 4

csc (-300) = csc 60 = 1/sin 60 = 2/sqrt 3 = 2 sqrt 3 /3

Answer 5

thanks alot..i was waiting for those two for a while now:)

Answer 6

I must respectfully note that Damon made a boo-boo.

the first question fits the pattern
cos(A+B) = cosAcosB - sinAsinB
then cos31deg*cos149-sin31deg*sin149
= cos(31+149)
= cos 180
= -1

Answer 7

thanks for that. i am going to try to get my assignment back, since i've already submitted it..:/