Answer: 70*sqrt(2)
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Step-by-step explanation:
One formula you can use is
A = b*c*sin(theta)
where angle theta is between sides b and c
Note how angle A is between sides AB = 10 and AD = BC = 14.
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Using that formula gives
A = b*c*sin(theta)
A = 10*14*sin(45)
A = 140*sin(45)
A = 140*sqrt(2)/2 ... use unit circle
A = (140/2)*sqrt(2)
A = 70*sqrt(2)