Question #475c4 Trigonometry Trigonometric Identities and Equations Fundamental Identities 1 Answer Anjali_Sharma Jan 9, 2017 Cos(90+x)= -sinx (because 90+x lies in second quadrant in which cos is negative and as it will change to -sinx) therefore sinx-(-sinx)=sinx+sinx+2sinx, hence proved. Answer link Related questions How do you use the fundamental trigonometric identities to determine the simplified form of the... How do you apply the fundamental identities to values of theta and show that they are true? How do you use the fundamental identities to prove other identities? What are even and odd functions? Is sine, cosine, tangent functions odd or even? How do you simplify sec xcos (frac{\pi}{2} - x )? If csc z = \frac{17}{8} and cos z= - \frac{15}{17}, then how do you find cot z? How do you simplify \frac{\sin^4 \theta - \cos^4 \theta}{\sin^2 \theta - \cos^2 \theta} using... How do you prove that tangent is an odd function? How do you prove that sec(pi/3)tan(pi/3)=2sqrt(3)? See all questions in Fundamental Identities Impact of this question 1627 views around the world You can reuse this answer Creative Commons License