Your vessel is on course 15°T, speed 17 knots. The apparent wind is from 40° off the starboard bow, speed 15 knots. What is the speed of true wind?
Given: Own course = 15°T
Own speed = 17 knots
Apparent wind bearing = 40°
Apparent wind speed = 15 knots
What is asked: True wind speed
Solution: Own speed² + Apparent wind speed² - 2 x Own speed x Apparent wind speed x Cos 40° and then square root the answer to get the true wind speed. This the formula to solving true wind speed:
True wind speed = √17² + 15² - 2 x 17 x 15 x Cos 40° = 11 knots
For a clearer picture of the formula, see image below.
Given: Own course = 15°T
Own speed = 17 knots
Apparent wind bearing = 40°
Apparent wind speed = 15 knots
What is asked: True wind speed
Solution: Own speed² + Apparent wind speed² - 2 x Own speed x Apparent wind speed x Cos 40° and then square root the answer to get the true wind speed. This the formula to solving true wind speed:
True wind speed = √17² + 15² - 2 x 17 x 15 x Cos 40° = 11 knots
For a clearer picture of the formula, see image below.
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