SOLUTION: could you please help me with this question
If x is in Quadrant IV with cos(x) = 3/5 and y is in Quadrant III with sin(y) = −2/√5, find cos(x+y)
I keep on gettin
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-> SOLUTION: could you please help me with this question
If x is in Quadrant IV with cos(x) = 3/5 and y is in Quadrant III with sin(y) = −2/√5, find cos(x+y)
I keep on gettin
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Question 1094865: could you please help me with this question
If x is in Quadrant IV with cos(x) = 3/5 and y is in Quadrant III with sin(y) = −2/√5, find cos(x+y)
I keep on getting -2√5 but that answer is not correct Found 3 solutions by ikleyn, basharat18, MathTherapy:Answer by ikleyn(52832) (Show Source):
1. "x is in Quadrant IV with cos(x) = 3/5" ====> sin(x) = = = .
The sign is "-" since sine is negative in QIV.
2. "y is in Quadrant III with sin(y) = " ====> cos(y) = = = .
The sign is "+" since cosine is negative in QIII.
3. cos(x+y) = cos(x)*cos(y) - sin(x)*sin(y) = = = = .
You can put this solution on YOUR website! COS (X+Y)= COSXCOSY-SINXSINY;
IF (a,b) be a position vector on xy plane .
sin(angle) = b/sqrroot( a^2 + b^2);
cos (angle)= a/sqrroot(a^2 +b^2);
according to question cosx = 3/5 (base/ hyp);
sinx = -4/5 (iv quad) ;
similarly siny= -2/sqrroot5;(per/hyp)
cosy= -1/sqrroot5;(base/hyp);
now cos(x+y)= (3/5)(-1/sqrroot5)-(-4/5)(-2/sqrroot5);
-11/5sqrroot5;
You can put this solution on YOUR website! could you please help me with this question
If x is in Quadrant IV with cos(x) = 3/5 and y is in Quadrant III with sin(y) = −2/√5, find cos(x+y)
I keep on getting -2√5 but that answer is not correct
cos (x + y) = cos x cos y - sin x sin y
Q IV
Q III
----- Easier to work with a RATIONALIZED denominator
------ Easier to work with a RATIONALIZED denominator
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