Q. The angle θ1 is located in QuadrantI, and sin(θ1)=21.What is the value of cos(θ1) ?Express your answer exactly.cos(θ1)=
Use Pythagorean Identity: We know that sin(θ1)=21 and θ1 is in Quadrant I. Use the Pythagorean identity sin2(θ)+cos2(θ)=1 to find cos(θ1). Substitute 21 for sin(θ1) in sin2(θ1)+cos2(θ1)=1. (21)2+cos2(θ1)=1.
Substitute and Simplify: Simplify (21)2+cos2(θ1)=1 to find the value of cos(θ1).41+cos2(θ1)=1cos2(θ1)=1−41cos2(θ1)=43
Take Square Root: Since we are looking for cos(θ1), we take the square root of both sides.cos(θ1)=±43cos(θ1)=±23
Determine Sign and Final Answer: Determine the sign of cos(θ1) based on the quadrant in which θ1 is located.Since θ1 is in Quadrant I, where both sine and cosine are positive, we choose the positive value for cos(θ1).cos(θ1)=3/2
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