use the law of cosines
x^2 = 6^2 + 6^2 - 2*6*6 cos100°
XYZ is an isosceles triangle . Line XY= line XZ=6cm and angle X = 100 . Calculate Lin YZ correct to 2 s.f
2 answers
After you make a sketch you will see that this is a simple case of
the cosine law:
YZ^2 = 6^2 + 6^2 - 2(6)(6)cos100
= 36 + 36 - 72(-12.503)
= 84.503
YZ = 9.19 cm r 9.2 cm to two significant figures.
or
drop a perpendicular from X, let the base be 2x
cos 40 = x/6
x = 6cos40
2x = 12cos40 = 9.19
the cosine law:
YZ^2 = 6^2 + 6^2 - 2(6)(6)cos100
= 36 + 36 - 72(-12.503)
= 84.503
YZ = 9.19 cm r 9.2 cm to two significant figures.
or
drop a perpendicular from X, let the base be 2x
cos 40 = x/6
x = 6cos40
2x = 12cos40 = 9.19