Writing x instead of theta, cos2x = 1 - (12/13)2 = 1 - 144/169 = 25/169 = (5/13)2
So cos(x) = ± 5/13
so that x = cos-1(5/13) or cos-1(-5/13)
And then, depending on the range of x, you have solutions for x. A calculator will only give you the principal solutions, though.
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1200/13 = 92.31%
Expressed in its simplest form, 3/4 x 12/13 = 9/13 or nine thirteenths.
Quadratic formula gives roots as 1.53 and 10.47 (to nearest hundredth.)
Without an "equals" word or sign somewhere, there is nothing to solve.You only have an expression, not an equation.
A dozen is twelve, so twelve dozen equals twelve times twelve.