Recall the double angle identity,
sin(2x) = 2 sin(x) cos(x)
Then we can write
sin(9x) cos(9x) = 1/2 sin(2 • 9x) = 1/2 sin(18x)
Then
∫ sin(9x) cos(9x) dx
= 1/2 ∫ sin(18x) dx
= -1/2 • 1/18 cos(18x) + C
= -1/36 cos(18x) + C
though you could continue with another double angle identity,
cos(2x) = cos²(x) - sin²(x)
to rewrite the antiderivative as
= -1/36 (cos²(9x) - sin²(9x)) + C
= 1/36 (sin²(9x) - cos²(9x)) + C
Answer:
Step-by-step explanation:
H
Answer:
k = 59.8
Step-by-step explanation:
Given
k - 7.8 = 52 ( isolate k by adding 7.8 to both sides )
k = 59.8
Answer:
9.54 cm
Explanation:
area = πr^2
286 cm^2= πr^2
=>πr^2= 286 cm^2
=>r^2= 286÷π
=>r= √286÷π
: 9.54. m
circumference=2πr
=> circumference=2×π×9.54
=60 cm
