Answer:
It's the law of cosines
Step-by-step explanation:
law of cosines states that 
so we know that a = 7, b = 4, and alpha would be 135 degrees, so just plugging it in gets us 49+16-2*7*4*(-0.707) = 65 + 39.59 = 104.59
X is 50. The lengths of the radii extending out from the center to the chords are the same length, therefore, the chords are the same distance from the center and have the same measure.
If x=8 {f(8)=3x+4}, the answer is 28.
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