Question

Find the perimeter of an isosceles triangle whose base is  40  cm and whose base angle is  70".

Answer 1

`cos70^0= (20)/(x)\\\\x= (20)/(cos70^0) \\\\the\ perimeter\ is:\\\\ P=2x+40=(40)/(cos70^0)+40 \ \ \ and\ \ \ cos70^0\approx0.3420\\\\P\approx(40)/(0.342)+40\approx156.96\ [cm]`

Answer 2

`cos70^o=(20)/(x)\\\\cos70^o\approx0.342\\\\(20)/(x)=0.342\\\\0.342x=20\ \ \ \ /:0.342\\\\x\approx58.5\ (cm)\\\\Perimeter:40cm+2\cdot58.5cm=157cm`