Posted by george on Tuesday, January 1, 2013 at 1:23pm.
14. Solve sin 2x + sin x = 0 for 0 ≤ x ≤ 2π.
21. Write 2sin37°sin26° as a sum (or difference).

trigonometry  Reiny, Tuesday, January 1, 2013 at 2:36pm
14.
sin 2x + sinx = 0
2sinxcosx + sinx = 0
sinx(2cosx + 1) = 0
sinx = 0 or sinx = 1/2
for sinx = 0
x = 0, π, 2π
for sinx = 1/2
x = 7π/6 or 11π/6 ( 210° or 330°)
21.
recall:
cos u  cosv = 2sin( (u+v)/2 ) sin( (uv)/2 )
let (u+v)/2 = 37 > u+v = 74
let (uv)/2= 26 > uv = 52
add them:
2u = 126
u = 63 , then v = 11
2 sin((63+11)/2) sin((6311)/2) = cos 63  cos 11
2 sin((63+11)/2) sin((6311)/2) = cos11°  cos63°
Answer This Question
Related Questions
 trigonometry  5. If cot 2θ = 5/12 with 0 ≤ 2θ ≤ π...
 Differentials (calc)  Solve the Poisson equation ∇^2u = sin(πx) for ...
 PRE  CALCULUS  Eliminate the parameter t. Find a rectangular equation for the ...
 Trigonometry  IM STUCK ON THESE :( 1. What is the equation for shifting the ...
 Trigonometry  IM STUCK ON THESE :( 1. What is the equation for shifting the ...
 Pre Calculus  sec x = 2 , π ≤ x ≤ 3π Use a calculator to...
 PreCalc  I'm not sure how to solve these with calculator. sec x = 2 , π...
 Trig  On the same set of axes, sketch and label the graphs of the equations y...
 algebra 1 help please  4) a student score is 83 and 91 on her first two quizzes...
 calculus  In spherical coordinates, the inequalities 0≤ρ≤2, 3...
More Related Questions