Show so that the expression of cos4A in term of SinA is 8Sin^4 - 8Sin^2A + 1
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If you notice the picture below
the composite figure is just a trapezoid sitting on top of a rectangle
and then, the rectangle has a triangular hole in it
so.. get the area of the trapezoid
then get the area of the rectangle, which is just a 12x14
and then get the area of the triangle, which surely you know is 1/2 bh
then, subtract the triangle's area from the rectangle's area
and whatever is left, namely the difference, add that to the area of the trapezoid, and that's the composite's area
namely the area of the trapezoid plus the rectangle's, minus the triangle's
the composite figure is just a trapezoid sitting on top of a rectangle
and then, the rectangle has a triangular hole in it
so.. get the area of the trapezoid
then get the area of the rectangle, which is just a 12x14
and then get the area of the triangle, which surely you know is 1/2 bh
then, subtract the triangle's area from the rectangle's area
and whatever is left, namely the difference, add that to the area of the trapezoid, and that's the composite's area
namely the area of the trapezoid plus the rectangle's, minus the triangle's
