Cosine And Sine Rule

Question 1

What is the algebraic formula for the COSINE rule using a, b and c for FINDING THE SIDE?

Note:
- a is side opposite angle A

Answer 1

a^2 = b^2 + c^2 - 2bc * cosA

Question 2

What is the algebraic formula for the COSINE rule using a, b and c for FINDING THE ANGLE

Note:
- a is side opposite angle A

Answer 2

cosA = (b^2 + c^2 - a^2) / 2bc

Question 3

When do you use the COSINE rule?

Answer 3

• (SAS) When you know two sides and the included angle (the angle between two sides)
• (SSS) When you know all three sides to find an angle

Question 4

What is the algebraic formula for the SINE rule using a, b and c for FINDING THE SIDE?

Note: a is side opposite angle A

Answer 4

a / sinA = b / sinB = c / sinC

Question 5

What is the algebraic formula for the SINE rule using a, b and c for FINDING THE ANGLE?

Note: a is side opposite angle A

Answer 5

sinA / a = sinB / b = sinC / c

Question 6

When do you use the SINE rule?

Answer 6

• (ASA or AAS) When you have 2 angles and one side
• (SSA) When you have two sides and a non-included angle (angle not between two sides)