How do you solve and find the value of cos(arctan(3/5))cos(arctan(35))?

1 Answer
Dec 23, 2016

cos(arctan(3/5))=5/sqrt34cos(arctan(35))=534

Explanation:

Let arctan(3/5)=thetaarctan(35)=θ

Hence tantheta=3/5tanθ=35

and cos(arctan(3/5))=costhetacos(arctan(35))=cosθ

= 1/sectheta1secθ

= 1/sqrt(sec^2theta)1sec2θ

= 1/sqrt(1+tan^2theta)11+tan2θ

= 1/sqrt(1+(3/5)^2)11+(35)2

= 1/sqrt(1+9/25)11+925

= 1/sqrt(34/25)13425

= sqrt(25/34)2534

= 5/sqrt34534