Warm Up 1) Find the height of the triangle below: 2) Find the area of the triangle below: A B C º °
9.2: Area of a Triangle
9.2 Area of a Triangle Objectives: 1.Find the area of a non-right triangle. Vocabulary: base, altitude, area, parallelogram, quadrilateral
The area A of a triangle equals one-half the product of two of its sides times the sine of its included angle. A = ½ absin(C) A = ½ acsin(B) A = ½ bcsin(A)
Find the area of the quadrilateral. A B C D 130º
9.4: Law of Cosines
8 Deriving the Law of Cosines Write an equation using Pythagorean theorem for shaded triangle. b h a k c - k ABAB C c
Note: capital letters always stand for __________! lower-case letters always stand for ________! When to use the Law of Cosines: SSS SAS angles sides A B C a b c The Law of Cosines!
Let’s do some problems! Ex. 1: Use the Law of Cosines to solve each triangle. Round any decimal answers to the nearest tenth. a ˚ B C A 19 a 57.3˚
b. E R D ˚ 108.2˚
T A C c 40˚ 53.0˚ Now you try!
Exit Slip Solve the triangle: p = 3, q = 8, <R = 50˚