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How to do this math problem, two models of original title, belt, high score reward, thank you, the teacher will punish you for copying the formula if you fail the exam, who can help?
Solution: 1)-3/4 (from known vectors OA = (1, 0), OB = (0, 1), OC = (2 Sina, cosA), from (OA+OB) * OC =/kloc-0.
2) AC = (2sina- 1, COSA), BC = (2sina, COSA- 1), because |ac|=|bc|, 4 s is after 2A+ 1-4 Sina+COS 2A = 4 s squared. Because A is in the third quadrant, sinA=- 1/ root 5, cosA=-2/ root 5, so SIN (A+PI/3) =1/2 * (1/root 5)+ root 3/2 *(2/).