If sec a + cos a = 5/2, then find sec a - cos a ? Trigonometry Right Triangles Relating Trigonometric Functions 1 Answer P dilip_k Feb 26, 2017 #(seca-cosa)^2=(seca+cosa)^2-4secaxxcosa# #=>(seca-cosa)^2=(5/2)^2-4xx1# #=>seca-cosa=sqrt(25/4-4)=sqrt(9/4)=3/2# Answer link Related questions What does it mean to find the sign of a trigonometric function and how do you find it? What are the reciprocal identities of trigonometric functions? What are the quotient identities for a trigonometric functions? What are the cofunction identities and reflection properties for trigonometric functions? What is the pythagorean identity? If #sec theta = 4#, how do you use the reciprocal identity to find #cos theta#? How do you find the domain and range of sine, cosine, and tangent? What quadrant does #cot 325^@# lie in and what is the sign? How do you use use quotient identities to explain why the tangent and cotangent function have... How do you show that #1+tan^2 theta = sec ^2 theta#? See all questions in Relating Trigonometric Functions Impact of this question 7863 views around the world You can reuse this answer Creative Commons License