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The angle 
theta_(1) is located in Quadrant IV, and 
sin(theta_(1))=-(13)/(85).
What is the value of 
cos(theta_(1)) ? Express your answer exactly.

cos(theta_(1))=

The angle θ1 \theta_{1} is located in Quadrant IV, and sin(θ1)=1385 \sin \left(\theta_{1}\right)=-\frac{13}{85} .\newlineWhat is the value of cos(θ1) \cos \left(\theta_{1}\right) ? Express your answer exactly.\newlinecos(θ1)= \cos \left(\theta_{1}\right)=

Full solution

Q. The angle θ1 \theta_{1} is located in Quadrant IV, and sin(θ1)=1385 \sin \left(\theta_{1}\right)=-\frac{13}{85} .\newlineWhat is the value of cos(θ1) \cos \left(\theta_{1}\right) ? Express your answer exactly.\newlinecos(θ1)= \cos \left(\theta_{1}\right)=
  1. Apply Pythagorean identity: Use the Pythagorean identity for sine and cosine.\newlineThe Pythagorean identity states that sin2(θ)+cos2(θ)=1\sin^2(\theta) + \cos^2(\theta) = 1.\newlineWe know sin(θ1)=1385\sin(\theta_{1}) = -\frac{13}{85}, so we can find cos2(θ1)\cos^2(\theta_{1}) using the identity.
  2. Calculate cos2(θ1)\cos^2(\theta_{1}): Calculate cos2(θ1)\cos^2(\theta_{1}).
    sin2(θ1)=(1385)2\sin^2(\theta_{1}) = \left(-\frac{13}{85}\right)^2
    sin2(θ1)=1697225\sin^2(\theta_{1}) = \frac{169}{7225}
    cos2(θ1)=1sin2(θ1)\cos^2(\theta_{1}) = 1 - \sin^2(\theta_{1})
    cos2(θ1)=11697225\cos^2(\theta_{1}) = 1 - \frac{169}{7225}
    cos2(θ1)=722572251697225\cos^2(\theta_{1}) = \frac{7225}{7225} - \frac{169}{7225}
    cos2(θ1)=70567225\cos^2(\theta_{1}) = \frac{7056}{7225}
  3. Find cos(θ1)\cos(\theta_{1}): Take the square root of cos2(θ1)\cos^2(\theta_{1}) to find cos(θ1)\cos(\theta_{1}).\newlineSince θ1\theta_{1} is in Quadrant IV, cosine is positive.\newlinecos(θ1)=70567225\cos(\theta_{1}) = \sqrt{\frac{7056}{7225}}\newlinecos(θ1)=8485\cos(\theta_{1}) = \frac{84}{85}

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