Using addition formulas for sine and cosine to simplify the expression:

cos (2pi/9) cos (pi/18) sin (2pi/9) sin(pi/18)

i want to learn it the normal way first before i add my instructors instructions to place s=45 & t = 30.

here are the formulas given:

sin(s t) = sin s cos t cos s sine t
sin(s-t) = sin s cos t - cos s sine t
cos(s t) = cos s cos t - sin s sin t
cos(s-t) = cos s cos t sin s sin t

the they way it looks, it seems to use formula 4:
cos(s-t) = cos s cos t sin s sin t

0

step-by-step explanation:

you can not divide by 0 so 4 ÷ 0 would be 0

0 × 9999 =0

mark brainliest   : )

step-by-step explanation:

i think something is missing in your question because y-1=(x-12) would not pass through the point (-4,-3). because if you replace x by -4 your are supposed to find y=-3 which is not the case her. if you replace x by -4 you find =-15.

i assume the right equation is y-1=1/4*(x-12) because this one is passing through both your points (if you are interested to know how i found that out i can tell you).

in this equation if i replace x by -4 i find y=-3 and if i replace x by 12, i find y=1 so the line representing this equation is passing through those 2 points.

then the standard form of the equation is finding an expression of y in function of x

y-1=1/4*(x-12)

y=x/4-3+1

y=x/4-2

hope that .

do you confirm there was a mistake in the question?