Formula Sheet for Test #2 You may have a Printed Copy Before You Start Your Test
Double Angle Formulas
sin 2 θ=2 sin θcos θ
cos 2 θ=cos2θ−sin2θ=1−2 sin2θ=2 cos2θ−1
tan 2 θ=2 tan θ
1−tan2θ
Half-Angle Formulas
sin α
2=±
√
1−cos α
2
cos α
2=±
√
1+cos α
2
tan α
2=±
√
1−cos α
1+cos α
=
1−cos α
sin α
=
sin α
1+cos α
The Law of Sines
a
sin A=b
sin B=c
sin C
Area of an Oblique SAS Triangle
Area=1
2
bc sin A=1
2
ab sin C=1
2
ac sin B
The Law of Cosines
a2=b2+c2−2bc cos A
Alternate forms
cos A=b2+c2−a2
2bc
b2=a+c2−2ac cos B
cos B=a2+c2−b2
2a c
c2=a2+b2−2ab cos C
cos C=a2+b2−c2
2ab
Heron’s Area Formula (Given SSS)
Area
¿
√
s(s−a)(s−b)( s−c)
, where a, b, and c are the sides and
s
is half of the perimeter of the triangle:
