What is the equation of the tangent line of #f(x) =sqrt(ln(sinx))# at # x = pi/4#? Calculus Derivatives Tangent Line to a Curve 1 Answer Wataru Apr 11, 2017 There is none. Explanation: Since #ln(sin(pi/4))=ln(1/sqrt{2})=-1/2 ln 2# is a negative number, #f(pi/4)# is not defined. Hence, there is no tangent line there. Answer link Related questions How do you find the equation of a tangent line to a curve? How do you find the slope of the tangent line to a curve at a point? How do you find the tangent line to the curve #y=x^3-9x# at the point where #x=1#? How do you know if a line is tangent to a curve? How do you show a line is a tangent to a curve? How do you find the Tangent line to a curve by implicit differentiation? What is the slope of a line tangent to the curve #3y^2-2x^2=1#? How does tangent slope relate to the slope of a line? What is the slope of a horizontal tangent line? How do you find the slope of a tangent line using secant lines? See all questions in Tangent Line to a Curve Impact of this question 1534 views around the world You can reuse this answer Creative Commons License