How do you find a numerical value of one trigonometric function of x given cotx+sinx=-cosxcotx? Trigonometry Trigonometric Identities and Equations Proving Identities 1 Answer Bdub Nov 12, 2016 :.x=+-pi+2pin Explanation: cotx+sinx=-cosxcotx cos x/sin x+sinx=-cosx cosx/sinx (cos x+sin^2x)/sinx=-cos^2x/sinx (cos x+sin^2x)/sinx *sinx=-cos^2x/sinx *sinx (cos x+sin^2x)/cancelsinx *cancelsinx=-cos^2x/cancelsinx *cancelsinx cos x+sin^2x=-cos^2x cos x+sin^2x+cos^2x=0 cosx+1=0 cosx=-1 x=cos^-1 (-1) :.x=+-pi+2pin Answer link Related questions What does it mean to prove a trigonometric identity? How do you prove \csc \theta \times \tan \theta = \sec \theta? How do you prove (1-\cos^2 x)(1+\cot^2 x) = 1? How do you show that 2 \sin x \cos x = \sin 2x? is true for (5pi)/6? How do you prove that sec xcot x = csc x? How do you prove that cos 2x(1 + tan 2x) = 1? How do you prove that (2sinx)/[secx(cos4x-sin4x)]=tan2x? How do you verify the identity: -cotx =(sin3x+sinx)/(cos3x-cosx)? How do you prove that (tanx+cosx)/(1+sinx)=secx? How do you prove the identity (sinx - cosx)/(sinx + cosx) = (2sin^2x-1)/(1+2sinxcosx)? See all questions in Proving Identities Impact of this question 2895 views around the world You can reuse this answer Creative Commons License