Find cos (2 A), if cos (A)=-frac{21}{29}, and A is in quadrant 3

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Accepted Answer

Step:1 ：Given that (cos(A) = -frac{21}{29}) and (A) is in quadrant 3Step:2 ：We know that the cosine of an angle in the third quadrant is negativeStep:3 ：We can use the formula for (cos(2A)), which is (2cos^2(A) - 1)Step:4 ：Substitute the given value of (cos(A)) into this formula to find (cos(2A))Step:5 ：(cos(2A) = 2(-frac{21}{29})^2 - 1)Step:6 ：Simplify to get (cos(2A) = 0.04875148632580273)Step:7 ：Final Answer: (boxed{0.04875148632580273})

Answer

Step: 1 ：Given that (cos(A) = -frac{21}{29}) and (A) is in quadrant 3Step: 2 ：We know that the cosine of an angle in the third quadrant is negativeStep: 3 ：We can use the formula for (cos(2A)), which is (2cos^2(A) - 1)Step: 4 ：Substitute the given value of (cos(A)) into this formula to find (cos(2A))Step: 5 ：(cos(2A) = 2(-frac{21}{29})^2 - 1)Step: 6 ：Simplify to get (cos(2A) = 0.04875148632580273)Step: 7 ：Final Answer: (boxed{0.04875148632580273})

Find $\cos (2 A)$ , if $\cos (A) = - \frac{21}{29}$ , and $A$ is in quadrant 3

Answer

Popular Problems

Find cos⁡(2A), if cos⁡(A)=−2129, and A is in quadrant 3

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Popular Problems

Find $\cos (2 A)$ , if $\cos (A) = - \frac{21}{29}$ , and $A$ is in quadrant 3