arccos(-0.8) ≈ 2.4981 radians or about 143.13 degreesarccos(π/4) ≈ 1.3258 radians or about 75.96 degreesarccos(0.6) ≈ 0.9273 radians or about 53.13 degrees
2)
arctan(21) ≈ 1.4966 radians or about 85.84 degreesarctan(8.9) ≈ 1.4601 radians or about 83.61 degreesarctan(-30) ≈ -1.5375 radians or about -88.18 degrees
1)
arccos(-0.8) ≈ 2.4981 radians or about 143.13 degreesarccos(π/4) ≈ 1.3258 radians or about 75.96 degreesarccos(0.6) ≈ 0.9273 radians or about 53.13 degrees2)
arctan(21) ≈ 1.4966 radians or about 85.84 degreesarctan(8.9) ≈ 1.4601 radians or about 83.61 degreesarctan(-30) ≈ -1.5375 radians or about -88.18 degrees