Join 60,000+ competitive exam aspirants
If cotθ=31,(0°<θ<90°), then the value of 1+cos2θ2−sin2θ+(csc2θ+sec2θ) is:
311
317
319
329
319
Since cot θ = 1/√3, identify θ = 60° immediately. Substitute θ = 60° into the expression: (2 - 3/4) / (1 + 1/4) + (4/3 + 4).
cot θ = 1/3 and 0° < θ < 90°.
cotθ=31⟹θ=60°, sin260°=43, cos260°=41, csc260°=34, sec260°=4
Since cot θ = 1/√3, identify θ = 60° immediately. Substitute θ = 60° into the expression: (2 - 3/4) / (1 + 1/4) + (4/3 + 4).
Students often struggle with the algebraic simplification of trig identities instead of directly calculating the values since θ is a standard angle.
Find the angle θ
Given cotθ=31. Since cot60°=31, we find θ=60°.
θ=60°
Evaluate the first part of the expression
Substitute θ=60° into 1+cos2θ2−sin2θ. With sin60°=23 and cos60°=21, we get 1+(41)2−(43)=4545=1.
1+412−43=1
Evaluate the second part of the expression
Calculate csc260°+sec260°. Since csc60°=32 and sec60°=2, the value is 34+4=316.
csc260°+sec260°=316
Final Sum
Add the two results: 1+316=33+16=319.
1+316=319
C is correct because the final calculated value of the expression is 19/3.
Always check if the given trig ratio corresponds to a standard angle (0°, 30°, 45°, 60°, 90°) to simplify the problem significantly.