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Projection rule
a = b cos C + c cos B
Where: B = base, C = angle C, a = side opposite A, b = side opposite B, c = side opposite C
Solved example
Given: B = 30°, C = 45°, b = 10, c = 4
Find: a (side opposite A)
- Formula: a = b·cos(C) + c·cos(B)
- Substitute the values: a = 10·cos(45°) + 4·cos(30°)
- Result: a = 10.535169
Answer: a = 10.535169
Calculator
How to calculate Projection rule
- Write down the formula: a = b cos C + c cos B.
- Note the known values (B, C, b, c).
- Substitute them and simplify to find a.
- Use the calculator above to solve for any letter.
Frequently asked questions
What is the formula for Projection rule?
The formula is a = b cos C + c cos B, where B = base, C = angle C, a = side opposite A, b = side opposite B, c = side opposite C.
What is Projection rule when B = 30°, C = 45°, b = 10, c = 4?
a = 10.535169. Substitute the values into a = b cos C + c cos B and simplify.