Can someone explain the approach they use for this question?
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You cannot calculate using 1, because we don’t know whether the two equal sides are sqrt(2) times the third one, or 1/sqrt(2) times the third one
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We again don’t know whether the sum of isosceles angles is 135, or the if it the sum of unequal angles
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If angles E and D sum to 90, then angle F is a right angle. In a right angled triangle, the hypotenuse can never be greater than the legs, thus the two equal sides are the legs of the triangle. Area of the triangle would be 1/2 x 3 x 3 = 4.5