Answer:
Choice B. sin(B)=cos(90-B)
Step-by-step explanation:
That cofunction identity is the one you looking for...choice B.
If you aren't convinced or don't know that identity, then maybe this will help:
90-B is actually the same thing as saying A for this right triangle since A+B=90.
So choice B basically says sin(B)=cos(A)
Well let's find both sin(B) and cos(A)
sin(B)=b/c
cos(A)=b/c
Those are the same ratios!
So they are equal!
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Answer:
x = π/4 and 5π/4
Step-by-step explanation:
Given the expression;
2cos²x - 1 = 0
2cos²x = 0+1
2cos²x = 1
cos²x = 1/2
cos x = ±√1/2
cos x = ±0.7071
x = arccos(±0.7071)
x = ±45 degrees
Convert to radians
Sence 180° = π rad
45° = x
x = 45π/180
x = π/4
If x = -45°
Since cos is negative in the 3rd quadrant
x = 180 + 45
x = 225°
x = 225π/180
x = 45π/36
x = 5π/4
-4x + 7y = 9 ⇒ -4x + 7y = 9 ⇒ 8x - 14y = -18
2y = -5x - 22 ⇒ -5x - 2y = 22 ⇒ <u>-35x - 14y = 154</u>
<u>43x</u> = <u>-172</u>
43 43
x = -4
-4x + 7y = 9
-4(-4) + 7y = 9
16 + 7y = 9
<u>- 16 - 16</u>
<u>7y</u> = <u>-7</u>
7 7
y = -1
(x, y) = (-4, -1)