Sederhanakan bentuk cos (100°+ x) cos (10°-x)+ sin(100°+x) sin (10°-x)

Cos(a-b)=cos a cos b + sin a sin b

cos (100°+ x) cos (10°-x)+ sin(100°+x) sin (10°-x)
a=100°+ x
b=10°-x
cos (100°+ x) cos (10°-x)+ sin(100°+x) sin (10°-x)
=cos(100+x-(10-x))
=cos(90+2x)
=-sin 2x

2(3x+7) + 2(2x+5) = 64 
6x+14+4x+10=64
10x + 24 = 64
10x = 64-24
10x = 40
x = 4

p = (3x + 7) = 12 + 7 = 19
l = (2x + 5) = 8 + 5 = 13

jawaban:

h gitu ya udah