IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Math => Topic started by: IO4567 on February 10, 2010, 03:54:44 pm

Title: C3 Trigonometry help!
Post by: IO4567 on February 10, 2010, 03:54:44 pm

Please could someone help me with this question... I've been at it for ages

Find, to 1 decimal place, the values of x , 0? x ? 360º, which satisfy the equation

2sinx = cos(x - 60)

Thank you!

Title: Re: C3 Trigonometry help!
Post by: astarmathsandphysics on February 10, 2010, 07:03:26 pm

2sinx = cos(x - 60)
2sinx=cosxcos60+sinxsin60
2sinx=1/2cosx+sqrt(3)/2 sinx
group the sinx terms
sinx(2-sqrt(3) /2)=1/2cosx
divide by cosx to get tanx=(1/2)/(2-sqrt(3) /2) so x=23.8 degress and 180+23.9=203.9