1)2[cos^2 20+cos^2 70/sin^2 25+sin^2 65]-tan 45+[tan13 tan23 tan30 tan67 tan77]
[ans. [3+sq.rt.3] / 3
2) sinA cosA - (sinA cos{90-A}cosA/sec{90-A})–(cosA sin{90-A}sinA/cosec{90-A})
[ans.0]
3)[–tanA cot{90-A}+secA cosec{90-A}+sin235+sin255] /[tan10 tan20 tan45 tan70 tan80] {ans.0}

PROVE
4) [1+tan^2 A] sinA cosA = tanA
5) sin^2 A cot^2 A + cos^2 A tan^2 A = 1
6) Find A if 07) sec^4 A-sec^2 A = tan^2 A + tan^4 A
8) [tan A + tan B]/[cot A + cot B ] = tanA tanB
9) [cosec A - sin A] [sec A - cos A] [tan A + cot A]=1
10) {[1+sinA]^2+[1-sinA]^2} / 2cos^2 A = [1+sin^2 A] /[1-sin^2 A]
11) 1/[sec A – tan A]= sec A+ tan A
12) Find A if 0 sin A / (1-cosA) + sinA / (1+cosA) = 4
13) Prove that sinA sin(90-A) – cosA cos(90-A) = 0
14) cos A/(1-sin A) + (1-sin A)/cos A = 2sec A
15) (1+ tan^2 A) (1+ cot^2 A)=1/(sin^2 A – sin^4 A)
16) (tan A + sec A -1)/(tan A - sec A+1) = (1 + sin A )/cosA
17) (sin A-sec A)^2 + (cos A-cosec A)^2 = (1- sec A cosec A)^2
18) 1/[sec A + tan A]-1/cos A = 1/cos A-1/[sec A- tan A]
19) [cot^2 A cosec^2 B]-[cot^2 B cosec^2 A] = cot^2 A-cot^2 B
20) For A=30, show that
Cos3A=4cos3A-3cosA

POSTED BY
NISHANT