Question

Find the exact value of sin(13pi/8)

Answer 1

Is one of your answer choices 0.03924146?

Answer 2

or 0.08893776

Answer 3

@chlomo_x3 a) (-sqrt2-sqrt2)/4
b) (sqrt2+sqrt2)/4
c) (sqrt2-sqrt2)/4
d) (-sqrt2+sqrt2)/4

Answer 4

Okay this will help me gimme one sec

Answer 5

okay thank you and i have two others... use the squared identities to simplify sin^2xsin^2x
a) 3+4cos(2x)+cos(4x)/8
b) 3-4cos(2x)+cos(4x)/8
c) 3+4cos(2x)-cos(4x)/8
d) 3-4cos(2x)-cos(4x)/8

if cosx=2/3 and x is in quadrant 4, then sinx/2=_____
a) -1/3
b)1/3
c)-sqrt1/6
d)sqrt1/6

Answer 6

sin(13pi/8) = -sin(16pi/8 - 13pi/8) = -sin(3pi/8) = -cos(4pi/8 - 3pi/8) = - cos(pi/8).

Use half angle formula for cos(x):
cos^2(x/2) = (cos(x) + 1) / 2
Let x = pi/4
cos^2(pi/8) = (cos(pi/4) + 1) / 2
cos^2(pi/8) = (sqrt(2) / 2 + 1) / 2
cos(pi/8) = sqrt(sqrt(2) / 4 + 1/2)

-cos(pi/8) = -sqrt((sqrt(2) + 2) / 4)

Answer 7

So the answer would be letter B

Answer 8

The second one

2(cos^2x) = 2[(1+cos2x)/2]^2
1/2 (1+2cos2x+cos^2(2x)=1/2(1+2cos2x+1+cos4x/2
=1/4(2=4cos2x+1+cos4x)= 3+4cos2x+cos4x/4

so letter A

Answer 9

thank you so much can you help with the last one @chlomo_x3