Given that sinx=21 and cosy=103, and that angles x and y are both in Quadrant I, find the exact value of sin(x−y), in simplest radical form.Answer:
Q. Given that sinx=21 and cosy=103, and that angles x and y are both in Quadrant I, find the exact value of sin(x−y), in simplest radical form.Answer:
Apply Sine Subtraction Formula: Use the sine subtraction formula: sin(x−y)=sin(x)cos(y)−cos(x)sin(y). We already know sin(x)=21 and cos(y)=103. Next, we need to find cos(x) and sin(y).
Find cos(x) and sin(y): Since x is in Quadrant I and sin(x)=21, we can use the Pythagorean identity sin2(x)+cos2(x)=1 to find cos(x). cos2(x)=1−sin2(x) cos2(x)=1−(21)2 cos2(x)=1−21 cos2(x)=21 sin(y)0, since cos(x) is positive in Quadrant I.
Substitute Values: Similarly, since y is in Quadrant I and cos(y)=103, we use the Pythagorean identity sin2(y)+cos2(y)=1 to find sin(y).sin2(y)=1−cos2(y)sin2(y)=1−(103)2sin2(y)=1−109sin2(y)=101sin(y)=101=101, since sin(y) is positive in Quadrant I.
Simplify Expression: Now we can substitute the values into the sine subtraction formula:sin(x−y)=sin(x)cos(y)−cos(x)sin(y)sin(x−y)=(21)(103)−(21)(101)
Rationalize Denominator: Simplify the expression:sin(x−y)=2103−2101sin(x−y)=2103−1sin(x−y)=2102
Rationalize Denominator: Simplify the expression:sin(x−y)=2103−2101sin(x−y)=2103−1sin(x−y)=2102Rationalize the denominator:sin(x−y)=2102×210210sin(x−y)=2×102210sin(x−y)=10210sin(x−y)=1020sin(x−y)=104×5sin(x−y)=1025sin(x−y)=55
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