What is the equation of the normal line of f(x)=1/sinx+cscx at x=pi/6?

1 Answer
Jan 4, 2017

y = 1/(4sqrt(3))x - (pi -96sqrt(3))/(24sqrt(3))

Explanation:

The function can be written as f(x) = cscx + cscx = 2cscx.

Start by finding the y-coordinate at the point of tangency.

f(pi/6) = 2csc(pi/6) = 2/sin(pi/6) = 2/(1/2) = 4

Differentiate.

f(x) = 2/sinx

f'(x) = (0 * sinx - 2 * cosx)/(sinx)^2

f'(x) = (-2cosx)/sin^2x

f'(x) = -2cotxcscx

You can find the slope of the tangent by inputting the point x =a into the derivative.

f'(pi/6) = -2cot(pi/6)csc(pi/6)

f'(pi/6) = -2/(tan(pi/6)sin(pi/6))

f'(pi/6) = -2/(1/sqrt(3) * 1/2)

f'(pi/6) = -2/(1/(2sqrt(3))

f'(pi/6) = -4sqrt(3)

The normal line is always perpendicular to the tangent. Therefore, its slope is given by the equation m_"normal" = -1/m_"tangent".

m_"normal" = -1/(-4sqrt(3))

m_"normal" = 1/(4sqrt(3))

The equation of the normal is therefore:

y - y_1 = m(x - x_1)

y - 4 = 1/(4sqrt(3))(x - pi/6)

y - 4= 1/(4sqrt(3))x - pi/(24sqrt(3))

y = 1/(4sqrt(3))x - (pi -96sqrt(3))/(24sqrt(3))

Hopefully this helps!