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The function 
f is defined by 
f(x)=x^(2)-5cos(2x). Use a calculator to write the equation of the line tangent to the graph of 
f when 
x=3. You should round all decimals to 3 places.
Answer:

The function f f is defined by f(x)=x25cos(2x) f(x)=x^{2}-5 \cos (2 x) . Use a calculator to write the equation of the line tangent to the graph of f f when x=3 x=3 . You should round all decimals to 33 places.\newlineAnswer:

Full solution

Q. The function f f is defined by f(x)=x25cos(2x) f(x)=x^{2}-5 \cos (2 x) . Use a calculator to write the equation of the line tangent to the graph of f f when x=3 x=3 . You should round all decimals to 33 places.\newlineAnswer:
  1. Calculate Derivative of f: To find the equation of the tangent line to the graph of ff at x=3x = 3, we need to calculate the derivative of ff, which will give us the slope of the tangent line at that point. The derivative of ff with respect to xx is f(x)=2x5derivative of cos(2x)f'(x) = 2x - 5 \cdot \text{derivative of } \cos(2x). The derivative of cos(2x)\cos(2x) with respect to xx is sin(2x)2-\sin(2x) \cdot 2 (using the chain rule). Therefore, f(x)=2x5(2sin(2x))=2x+10sin(2x)f'(x) = 2x - 5 \cdot (-2\sin(2x)) = 2x + 10\sin(2x).
  2. Evaluate Derivative at x=3x=3: Now we need to evaluate the derivative at x=3x = 3 to find the slope of the tangent line. So we calculate f(3)=2(3)+10sin(23)f'(3) = 2(3) + 10\sin(2\cdot 3). Using a calculator, we find that sin(6)\sin(6) is approximately 0.279-0.279. Therefore, f(3)6+10(0.279)=62.79=3.21f'(3) \approx 6 + 10(-0.279) = 6 - 2.79 = 3.21.
  3. Find y-coordinate at x=3x=3: Next, we need to find the y-coordinate of the point on the graph of ff where x=3x = 3. We do this by evaluating f(3)=325cos(23)f(3) = 3^2 - 5\cos(2\cdot 3). Using a calculator, we find that cos(6)\cos(6) is approximately 0.9600.960. Therefore, f(3)95(0.960)=94.8=4.2f(3) \approx 9 - 5(0.960) = 9 - 4.8 = 4.2.
  4. Write Equation of Tangent Line: With the slope of the tangent line m=3.21m = 3.21 and the point on the graph (3,4.2)(3, 4.2), we can use the point-slope form of the equation of a line to write the equation of the tangent line. The point-slope form is yy1=m(xx1)y - y_1 = m(x - x_1), where mm is the slope and (x1,y1)(x_1, y_1) is the point on the line. Plugging in our values, we get y4.2=3.21(x3)y - 4.2 = 3.21(x - 3).
  5. Convert to Slope-Intercept Form: Finally, we simplify the equation to put it in slope-intercept form y=mx+by = mx + b. We distribute the slope on the right side of the equation and then add 4.24.2 to both sides to solve for yy. y4.2=3.21x9.63y - 4.2 = 3.21x - 9.63. Adding 4.24.2 to both sides gives us y=3.21x9.63+4.2y = 3.21x - 9.63 + 4.2. Simplifying further, y=3.21x5.43y = 3.21x - 5.43.

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