I have a lot of Geometry homework:/ help me please

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To find the inverse of a number a, one can use the equation f(c) = a-1/c=0 where c is the inverse of a use the secant method of finding roots of equations to find the inverse of a = 2.5 ,er = 0.001%

Find the measure of angle c in the following triangle.

The graph shows the amount of total rainfall at each hour what was the total rainfall amount after three hours