Answer:
about 1.56637 radians ≈ 89.746°
Step-by-step explanation:
The reference angle in radians can be found by the formula ...
ref angle = min(mod(θ, π), π -mod(θ, π))
Equivalently, it is ...
ref angle = min(ceiling(θ/π) -θ/π, θ/π -floor(θ/π))×π
When we divide 11 radians by π, the result is about 3.501409. The fractional part of this quotient is more than 1/2, so the reference angle will be ...
ref angle = (1 -0.501409)π radians ≈ 1.56637 radians ≈ 89.746°
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Additional comment
For calculations such as this, you need to use the most accurate value of pi available. The approximations 22/7 or 3.14 are not sufficiently accurate to give good results.
