Question 234134
BIG TIP: Post one question at a time or else no one will reply. 
1.Given that sin0=4/5 and 0 lies in quadrant ll,find the following value, cos 0. 
The first thing to know is that the sine function is positive in quadrant 2 but the cosine function is negative in that quadrant. 
Also, sine = opposite/hypotense and cosine = adjacent/hypotenuse. 
So, sin (0) = 4/5 means that the opposite side of this right triangle in quadrant 2 is 4 and its hypotenuse is 5. We now use the Pythagorean Theorem to find the other leg of the right triangle. 
(4)^2 + (leg)^2 = (5)^2 
16 + (leg)^2 = 25 
(leg)^2 = 25 - 16 
(leg)^2 = 9 
leg = 3 
Now, that we know the other leg of the right triangle is 3, we use that information to find cos (0). 
Like I said above, cosine = adjacent/hypotenuse. 
Then, cos(0) = 3/5. 
However, since cosine is negative in quadrant 2, the answer is cos(0) = -3/5 
Follow this same logic to answer the rest of your questions or post one question at a time.