lawrence's holiday blog 1

we learned the first part of chapter 10. it is really easy. just know the formula and plug in.

formulas:

cos(alpha + or - beta) =sine alpha cos beta - or + sin alpha cos beta

sin (alpha + or - beta)= sin alpha cos beta + or - cos alpha sin beta


* aplha and beta come from the trig chart and add or subtract to get the angle you are looking for.


ex. find the exact value of sin 15

alpha= 45
beta= 30

sin(45-30)= sin45 cos30- cos45 sin 30

square root of2/2 square root of3/2 - square root of2/2 1/2

square root of6/4- square root of2/4 = square root of 6-2/f


ex.2

suppose that sin alpha=4/5 and sin beta= 5/13. where 0
cos alpha cos beta- sinalpha sin beta

(3/5)(-12/13)- (4/5)(5/13)

(-36/65)-(20/65)

(-56/65)



that is all that i learned in chapter 10 section 1. i hope this helped out the people who dont understand even though i dont know how you wont get this section when it is the easiest thing we probably will cover.