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If 
cos x=(3)/(5),x in quadrant 
I, then find (without finding 
x )

{:[sin(2x)=],[cos(2x)=],[tan(2x)=]:}

If cosx=35,x \cos x=\frac{3}{5}, x in quadrant I I , then find (without finding x x )\newlinesin(2x)=cos(2x)=tan(2x)= \begin{array}{l} \sin (2 x)= \\ \cos (2 x)= \\ \tan (2 x)= \end{array}

Full solution

Q. If cosx=35,x \cos x=\frac{3}{5}, x in quadrant I I , then find (without finding x x )\newlinesin(2x)=cos(2x)=tan(2x)= \begin{array}{l} \sin (2 x)= \\ \cos (2 x)= \\ \tan (2 x)= \end{array}
  1. Apply Double Angle Formulas: Use the double angle formulas for sine and cosine:\newlinesin(2x)=2sin(x)cos(x)\sin(2x) = 2\sin(x)\cos(x)\newlinecos(2x)=cos2(x)sin2(x)\cos(2x) = \cos^2(x) - \sin^2(x)\newlinetan(2x)=sin(2x)cos(2x)\tan(2x) = \frac{\sin(2x)}{\cos(2x)}
  2. Find sin(x)\sin(x): Find sin(x)\sin(x) using the Pythagorean identity, sin2(x)+cos2(x)=1\sin^2(x) + \cos^2(x) = 1:sin2(x)=1cos2(x)=1(35)2=1925=1625\sin^2(x) = 1 - \cos^2(x) = 1 - \left(\frac{3}{5}\right)^2 = 1 - \frac{9}{25} = \frac{16}{25}sin(x)=1625=45\sin(x) = \sqrt{\frac{16}{25}} = \frac{4}{5} (since xx is in quadrant I, sin(x)\sin(x) is positive)
  3. Calculate sin(2x)\sin(2x) and cos(2x)\cos(2x): Calculate sin(2x)\sin(2x) and cos(2x)\cos(2x) using the values of sin(x)\sin(x) and cos(x)\cos(x):sin(2x)=2×(45)×(35)=2425\sin(2x) = 2 \times \left(\frac{4}{5}\right) \times \left(\frac{3}{5}\right) = \frac{24}{25}cos(2x)=(35)2(45)2=9251625=725\cos(2x) = \left(\frac{3}{5}\right)^2 - \left(\frac{4}{5}\right)^2 = \frac{9}{25} - \frac{16}{25} = -\frac{7}{25}
  4. Calculate tan(2x)\tan(2x): Calculate tan(2x)\tan(2x) using sin(2x)\sin(2x) and cos(2x)\cos(2x):tan(2x)=2425/725=247\tan(2x) = \frac{24}{25} / \frac{-7}{25} = -\frac{24}{7}

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