Hello !
cos (a+b) = cos a cos b - sin a sin b
sin (a+b) = sin a cos b + sin b cos a
cos (a+b+c) = cos (a+(b+c))
cos (a+b+c) = cos a cos (b+c) - sin a sin (b+c)
cos (a+b+c) = cos a (cos b cos c - sin b sin c) - sin a (sin b cos c + sin c cos b)
cos (a+b+c)=cos a cos b cos c - cos a sin b sin c - sin a sin b cos c - sin a cos b sin c
Answer: -5x-8y=-5
Step-by-step explanation:
add right sides of equation and even them with result of adding right sides of equation
4x-4y-9x-4y=-2-3
-5x-8y=-5
Answer:
x = -5
Step-by-step explanation:
Reduce the expression by cancelling the common factors: 1/n
