How do you find sin if tan=2? Trigonometry Right Triangles Relating Trigonometric Functions 1 Answer Nghi N. Nov 27, 2015 Find sin x knowing tan x = 2 Ans: #+- (2sqrt5)/5# Explanation: Use the trig identity: #sin^2 x = 1/(1 + cot^2 x)# #tan x = 2# --> #cot x = 1/2# --> #cot^2 x = 1/4# #sin^2 x = 1/(1 + 1/4) = 1/(5/4) = 4/5# #sin x = +- 2/sqrt5 = +- (2sqrt5)/5# 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 19672 views around the world You can reuse this answer Creative Commons License