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In the triangle ABC, the bisector of angle B and angle c is called point O. if angle a is equal to 40 degrees, then how many degrees is angle BOC equal to Right now!
Connect Ao to BC to M
∠BOM+∠COM=1/2(∠ABC+∠ACB+∠BCA)
∠BOM+∠COM=∠BAC+1/2（180°-∠BAC）
That is, BOC = 40 ° + 70 ° = 110 °
It is known that in △ ABC, ∠ a = 60 ° and the bisectors of ∠ ABC and ∠ ACB intersect at point O, then the degree of ∠ BOC is 0______ Degree
∵∠A=60°∴∠ABC+∠ACB=120°∴∠BOC=180°-12（∠ABC+∠ACB）=120°．
In the straight triangular prism abc-a1b1c1, if ∠ BAC = 90 ° AB = AC = Aa1, then the angle between the out of plane straight line BA1 and AC1 is equal to ()
A. 30°B. 45°C. 60°D. 90°
Extend CA to D, so that ad = AC, then ada1c1 is a parallelogram, ∠ da1b is the angle formed by the out of plane straight line BA1 and AC1, and a1d = A1B = DB = 2Ab, then the triangle a1db is an equilateral triangle, ∧ da1b = 60 ° so select C
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