Homework Sourse4 pts lfx 4 5 sin for 0 Solutionx 4 5 sin theta sin thet
(4 pts) lfx + 4 = 5 sin() for 0 
Solution
x + 4 = 5 sin theta
sin theta = ( x+4) / 5
cos theta = sqrt ( 5^2 - (x+4)^2 ) / 5
= sqrt ( -x^2 + 8x + 9 ) / 5
cos (2 theta ) = cos^2 theta - sin^2 theta
cos ( 2 theta ) = {sqrt ( 5^2 - (x+4)^2 ) / 5}^2 - { ( x+4) / 5 }^2
= ( -x^2 + 8x + 9 ) / 25 - (x^2 + 8x + 16) / 25
= ( -2x^2 - 7 ) / 25
cos (2 theta ) = -( 2x^2 + 7 )/ 25
