I need help on this question:
Q) Calculate without using a calculator the exact value of
√3 cos15 - sin15
Ans) √2
can someone show me the working of it. Thx!
(the equation isnt equal to 0 or anything)
Use the half angle formulas: 4. Half Angle Formulas
What have you covered already? As far as I'm aware the two solutions proposed by Mr F are the best/only methods:
$\displaystyle cos(A \pm B) = cosAcosB \mp sinAsinB$
$\displaystyle sin (A \pm B) = sinAcosB \pm cosAsinB$
unless you're more familiar with that form.
(The half angle formulae are also derived from that form because cosA = cos(0.5A+0.5A))