Dom Dom's blog

A little bit of chapter 10

Section 1:
Finding exact values of si and cos and other stuff. I understood this pretty well, just remember the formulas and the trig chart and you'll be fine.
ex. Find the exact value of sin 75
=sin (45 + 30) = sin45cos30 + cos45 sin30
= (1/2)(sqrt2/2) + (sqrt3/2)(sqrt2/2)
= (sqrt6 + sqrt2)/4
Section 2:
Same thing as section 1, but with tan and cot. Again, formulas and trig chart.
ex. Find the exact value of tan 15
=tan (45 - 15) = tan45 - tan15/1 + tan45 tan 15
= (sqrt3/3) - 1/1 + (sqrt3/3)(1)
= (sqrt3) -3/(sqrt3) + 3
= 2 - (sqrt3)
Section 3:
Double and Half-Angle formulas. Like, sin2A and cos2A and all that other nonsense.
ex. 2sin45 cos45
Sin2A formula = 2sinAcosA
So, sin2A = sin2(45)
= sin 90 = 1