- Suppose sin(A) =2/5. Use the trig identity sin^2 (A) + cos^2 (A) =1 to find cos(A) in quadrant I. Round to ten-thousandth.

Step-by-step explanation:

SinA=2/5

sin²A=4/25

cos²A=1-4/25

cos²A=21/25

cosA=±✓21/5

cosA=±0.9165

none of the above.

for one of the equations to be used in the process, there has to be a term in the equation since squared is .

since there is only a term in the first equation, we cannot derive a from completing the square.

solving with completing the square